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>
# include <string.h>

int main() {
    int n;
    scanf("%d", &n);
    int vec[n];
    
    for (int i = 0; i < n; ++i)
        scanf("%d", &vec[i]);
    int a =0;
    for (int i = 0; i < n; ++i){
        int cont = 0;
        for (int j = 0; j < n; ++j){
            if (vec[i] == vec[j]){
                cont += 1;
                //printf("--%d", cont);
            }
        }
        if (cont > 1){
            a = 1;
            break;
            
        }
    }
    if ( a == 1)
        printf("NO\n");
    else
        printf("YES\n");
    


    return 0;
}