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: def merge(l, r, a):
      l1 = len(l)
      r1 = len(r)
      i, j, k = 0, 0, 0
      while j < l1 and k < r1:
          if l[j] < r[k]:
              a[i] = l[j]
              j += 1
          elif l[j] == r[k]:
              a[i] = l[j]
              j += 1
              global res
              print("NO")
              quit()
              return 0
          else:
              a[i] = r[k]
              k += 1
          i += 1
      while j < l1:
          a[i] = l[j]
          j += 1
          i += 1
      while k < r1:
          a[i] = r[k]
          k += 1
          i += 1
      return a
  
  
  def mergeSort(a):
      n = len(a)
      if n == 1:
          return a
      else:
          mid = n // 2
          left = []
          right = []
          for i in range(mid):
              left.append(a[i])
          for i in range(mid, n):
              right.append(a[i])
          mergeSort(left)
          mergeSort(right)
          merge(left, right, a)
          return a
  
  
  n = int(input())
  a = list(map(int, input().split()))
  res = True
  s = mergeSort(a)
  if res:
      print("YES")
  else:
      print("NO")
  
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"}]