output_description: Print x_{N,1}.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N
      a_1a_2\ldotsa_N
attempt: n = int(input())
  s = input()
  if set(list(s)) == {"1", "3"}:
      print(2)
  
problem_description: Statement
  
  Given is a sequence of N digits a_1a_2\ldots a_N, where each element is 1, 2,
  or 3. Let x_{i,j} defined as follows:
  
    * x_{1,j} := a_j \quad (1 \leq j \leq N)
    * x_{i,j} := | x_{i-1,j} - x_{i-1,j+1} | \quad (2 \leq i \leq N and 1 \leq j \leq N+1-i)
  
  Find x_{N,1}.
samples: [{"input": "4\n    1231", "output": "1\n    \n\nx_{1,1},x_{1,2},x_{1,3},x_{1,4} are respectively 1,2,3,1.\n\nx_{2,1},x_{2,2},x_{2,3} are respectively |1-2| = 1,|2-3| = 1,|3-1| = 2.\n\nx_{3,1},x_{3,2} are respectively |1-1| = 0,|1-2| = 1.\n\nFinally, x_{4,1} = |0-1| = 1, so the answer is 1.\n\n* * *"}, {"input": "10\n    2311312312", "output": "0"}]