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(void){
    int i,k,n,a,b,c;
    int array1[100][100][20];
    scanf("%d",&n);
    for(i=0;i<n;i++){
        a=i%100;
        b=(i/100)%100;
        c=i/10000;
        scanf("%d",&array1[a][b][c]);
        //compare
        for(k=0;k<i;k++){
            if(array1[k%100][(k/100)%100][k/10000]==array1[a][b][c]){
                printf("NO\n");
                return 0;
            }
        }
    }
    printf("YES\n");
    return 0;
}