output_description: Print the answer.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N i
attempt: N = int(input())
  A = list(map(int, input().split()))
  median_len = N * (N + 1) // 2
  median = median_len // 2 + 1
  a = 1
  medin_rank = 1
  for i in range(1, N):
      a = i * (i + 1) // 2
      b = (i + 2) * (i + 1) // 2
      if a <= median and b > median:
          medin_rank = i
          break
  rank_index = median - a
  median_list = []
  l = medin_rank // 2
  for i in range(N - medin_rank):
      median_list.append(A[l + i])
  print(median_list[rank_index])
  
problem_description: Statement
  
  There is an N-car train.
  
  You are given an integer i. Find the value of j such that the following
  statement is true: "the i-th car from the front of the train is the j-th car
  from the back."
samples: [{"input": "4 2", "output": "3\n    \n\nThe second car from the front of a 4-car train is the third car from the back.\n\n* * *"}, {"input": "1 1", "output": "1\n    \n\n* * *"}, {"input": "15 11", "output": "5"}]