| Schedule of changes in the number of shares of common stock under option | 
 
		
			
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						Stock Options 
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				| 
					 
						Outstanding at December 29, 2016 
				 | 
				
					 
						  
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						 11,979,111 
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				| 
					 
						Granted  
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						 1,272,156 
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				| 
					 
						Exercised  
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				 | 
				
					 
						 (1,004,322) 
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				| 
					 
						Forfeited or expired  
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						 (159,687) 
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				| 
					 
						Outstanding at September 28, 2017 
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						 12,087,258 
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						Options 
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						Weighted Average Exercise Price 
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						Options Exercisable at End of Year 
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						Weighted Average Exercise Price of Exercisable Options 
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						Weighted Average Fair Value/Share of Options Granted During the Year 
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				| 
					 
						Outstanding at December 26, 2013 
				 | 
				
					 
						  
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10,714,356
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						$ 
				 | 
				
4.09
				 | 
				
					 
						  
				 | 
				
					 
						  
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3,471,150
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						$ 
				 | 
				
3.64
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						— 
				 | 
				
					 
						  
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				| 
					 
						Granted 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
748,553
				 | 
				
					 
						  
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						$ 
				 | 
				
7.69
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						— 
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				 | 
				
					 
						  
				 | 
				
					 
						— 
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						$ 
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3.72
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				| 
					 
						Exercised 
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(201,137
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						) 
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						$ 
				 | 
				
3.28
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				 | 
				
					 
						  
				 | 
				
					 
						— 
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				 | 
				
					 
						  
				 | 
				
					 
						— 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						— 
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				 | 
			 
			
				| 
					 
						Forfeited or expired 
				 | 
				
					 
						  
				 | 
				
					 
						  
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(1,737,506
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						) 
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						$ 
				 | 
				
4.06
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				 | 
				
					 
						— 
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						— 
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						— 
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				| 
					 
						 
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						Outstanding at December 25, 2014 
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9,524,266
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						$ 
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4.40
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4,608,462
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						$ 
				 | 
				
3.85
				 | 
				
					 
						  
				 | 
				
					 
						  
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						— 
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				| 
					 
						Granted 
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1,378,355
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						$ 
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8.07
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						— 
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				 | 
				
					 
						  
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						— 
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						$ 
				 | 
				
4.12
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				| 
					 
						Exercised 
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(5,149
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						) 
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						$ 
				 | 
				
7.69
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						— 
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						— 
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						— 
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				| 
					 
						Forfeited or expired 
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(437,353
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						) 
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						$ 
				 | 
				
7.16
				 | 
				
					 
						  
				 | 
				
					 
						  
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						— 
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				 | 
				
					 
						  
				 | 
				
					 
						— 
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						— 
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				| 
					 
						 
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						Outstanding at December 31, 2015 
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10,460,119
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						$ 
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4.77
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6,656,524
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						$ 
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4.00
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						— 
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				| 
					 
						Granted 
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2,025,535
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						$ 
				 | 
				
9.94
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						— 
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						— 
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						$ 
				 | 
				
4.13
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						Exercised 
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(145,140
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						) 
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						$ 
				 | 
				
3.48
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				 | 
				
					 
						— 
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				 | 
				
					 
						  
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						— 
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				 | 
				
					 
						  
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						— 
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Forfeited or expired 
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				 | 
				
					 
						  
				 | 
				
(361,403
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						) 
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						$ 
				 | 
				
6.65
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				 | 
				
					 
						  
				 | 
				
					 
						— 
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				 | 
				
					 
						  
				 | 
				
					 
						— 
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						— 
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				| 
					 
						 
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				| 
					 
						Outstanding at December 29, 2016 
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11,979,111
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						$ 
				 | 
				
5.34
				 | 
				
					 
						  
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8,151,056
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				 | 
				
					 
						$ 
				 | 
				
4.20
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						— 
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				| 
					 
						 
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