Problem:
Score : 300 points

Problem Statement

Given is a sequence of integers A_1, A_2, ..., A_N.
If its elements are pairwise distinct, print YES; otherwise, print NO.

Constraints

2 ≤ N ≤ 200000

1 ≤ A_i ≤ 10^9

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N
A_1 ... A_N

Output

If the elements of the sequence are pairwise distinct, print YES; otherwise, print NO.

Sample Input 1

5
2 6 1 4 5

Sample Output 1

YES

The elements are pairwise distinct.

Sample Input 2

6
4 1 3 1 6 2

Sample Output 2

NO

The second and fourth elements are identical.

Sample Input 3

2
10000000 10000000

Sample Output 3

NO

Solution in Python (3.4.3) (judge verdict: Accepted)

# -*- coding: utf-8 -*-
"""
Created on Wed Mar  4 17:14:33 2020

@author: Kanaru Sato
"""

N = int(input())
A = input().split()

D = {}

for i in range(0,N):
    if A[i] not in D:
        D[A[i]] = 1
    elif A[i] in D:
        D[A[i]] += 1
        

flag = 0

for i in list(D.values()):
    if i > 1:
        flag = 1
        break
    elif i <= 1:
        continue

if flag==0:
    print("YES")
else:
    print("NO")