import os, sys, re, math

N = int(input())
A = [int(n) for n in input().split()]

A = sorted(A)
answer = 'YES'
for i in range(1, len(A)):
    if A[i - 1] == A[i]:
        answer = 'NO'
        break

print(answer) import os, sys, re, math os sys re math N = int(input()) N int(input()) int input() input int(n) for n in input().split() for n in input().split() n input().split() ().split () input split for n in input().split() int(n) int n A = [int(n) for n in input().split()] A [int(n) for n in input().split()] A = sorted(A) A sorted(A) sorted A answer = 'YES' answer 'YES' for i in range(1, len(A)):
    if A[i - 1] == A[i]:
        answer = 'NO'
        break i range(1, len(A)) range 1 len(A) len A if A[i - 1] == A[i]:
        answer = 'NO'
        break A[i - 1] == A[i] A[i - 1] A i - 1 i 1 A[i] A i answer = 'NO' answer 'NO' break print(answer) print answer A = [int(n) for n in input().split()] [int(n) for n in input().split()] A A = sorted(A) sorted(A) A answer = 'YES' 'YES' answer answer = 'NO' 'NO' answer N = int(input()) int(input()) N
import os, sys, re, math

N = int(input())
A = [int(n) for n in input().split()]

A = sorted(A)
answer = 'YES'
for i in range(1, len(A)):
    if A[i - 1] == A[i]:
        answer = 'NO'
        break

print(answer)
