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: # -*- coding: utf-8 -*-
  
  import sys
  
  
  def input():
      return sys.stdin.readline().strip()
  
  
  def list2d(a, b, c):
      return [[c] * b for i in range(a)]
  
  
  def list3d(a, b, c, d):
      return [[[d] * c for j in range(b)] for i in range(a)]
  
  
  def list4d(a, b, c, d, e):
      return [[[[e] * d for j in range(c)] for j in range(b)] for i in range(a)]
  
  
  def ceil(x, y=1):
      return int(-(-x // y))
  
  
  def INT():
      return int(input())
  
  
  def MAP():
      return map(int, input().split())
  
  
  def LIST(N=None):
      return list(MAP()) if N is None else [INT() for i in range(N)]
  
  
  def Yes():
      print("Yes")
  
  
  def No():
      print("No")
  
  
  def YES():
      print("YES")
  
  
  def NO():
      print("NO")
  
  
  sys.setrecursionlimit(10**9)
  INF = 10**18
  MOD = 10**9 + 7
  
  N = INT()
  A = LIST()
  
  if len(A) == len(set(A)):
      YES()
  else:
      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"}]