import sys

n = int(input())
a = dict()
for x in map(int, input().split()):
  if a.get(x) == 1:
    print('NO')
    sys.exit()

  a[x] = 1

print('YES') import sys sys n = int(input()) n int(input()) int input() input a = dict() a dict() dict for x in map(int, input().split()):
  if a.get(x) == 1:
    print('NO')
    sys.exit()

  a[x] = 1 x map(int, input().split()) map int input().split() ().split () input split if a.get(x) == 1:
    print('NO')
    sys.exit()

   a.get(x) == 1 a.get(x) a.get a get x 1 print('NO') print 'NO' sys.exit() sys.exit sys exit a[x] = 1 a[x] a x 1 print('YES') print 'YES' n = int(input()) int(input()) n a = dict() dict() a
import sys

n = int(input())
a = dict()
for x in map(int, input().split()):
  if a.get(x) == 1:
    print('NO')
    sys.exit()

  a[x] = 1

print('YES')
