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 check(int a[], int n){
    int i, j;
    for(i=1;i<n;i++){
        for(j=0;j<i;j++){
            if(a[i]==a[j])  return 0;
        }
    }
    return 1;
}

int main(){
    int n,i;
    scanf("%d",&n);

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

    if(check(a,n))  printf("YES");
    else    printf("NO");

    return 0;
}