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 C (GCC 5.4.1) (judge verdict: Time Limit Exceeded)

#include<stdio.h>

int main()
{
    int n, a[200000], i;
    int j=0, k;
    scanf("%d", &n);
    for(i=0; i<n; i++){
        scanf("%d", &a[i]);
        k=i;
        for(j=0; j<i; j++){
            if(k!=j && a[k]==a[j]){
                printf("NO\n");
                goto end;
            }
        }
    }
    
    printf("YES\n");
    end :
    return 0;
}