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: Accepted)

#include <stdio.h>
#include <stdlib.h>

int comp(const void *a, const void *b){
    return *(int*)a-*(int*)b;
}

int main(void)
{
    int i, n, a[200001];
    scanf("%d", &n);

    for( i = 0; i < n; i++ ){
        scanf("%d", &a[i]);
    }

    qsort(a, n, sizeof(int), comp);

    for( i = 0; i < n-1; i++ ){
        if( a[i] == a[i+1] ){
            printf("NO\n");
            return 0;
        }
    }
    printf("YES\n");
    return 0;
}