5 lines
		
	
	
		
			241 B
		
	
	
	
		
			Python
		
	
	
	
	
	
			
		
		
	
	
			5 lines
		
	
	
		
			241 B
		
	
	
	
		
			Python
		
	
	
	
	
	
| nums = sorted([int(l) for l in open("input", "r").read().split("\n") if l])
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| nums = [0] + nums + [nums[-1]+3]
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| diffs = [b - a for (a, b) in zip(nums[:-1], nums[1:])]
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| print(len([n for n in diffs if n == 1]) * len([n for n in diffs if n == 3]))
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