output_description: If the elements of the sequence are pairwise distinct, print `YES`; otherwise,
  print `NO`.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N
      A_1 ... A_N
attempt: N, K = map(int, input().split())
  p = list(map(int, input().split()))
  max = 0
  for i in range(N - K + 1):
      s = 0
      for j in range(i, i + K):
          s += p[j]
      if s > max:
          max = s
  print((max + K) / 2)
  
problem_description: Statement
  
  Given is a sequence of integers A_1, A_2, ..., A_N. If its elements are
  pairwise distinct, print `YES`; otherwise, print `NO`.
samples: [{"input": "5\n    2 6 1 4 5", "output": "YES\n    \n\nThe elements are pairwise distinct.\n\n* * *"}, {"input": "6\n    4 1 3 1 6 2", "output": "NO\n    \n\nThe second and fourth elements are identical.\n\n* * *"}, {"input": "2\n    10000000 10000000", "output": "NO"}]