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 9.2.1) (judge verdict: Wrong Answer)

#include<stdio.h>
#include<stdlib.h>
#include<math.h>
#define rep(i,n) for(i=0;i<n;i++)
#define PI 3.14159265358979323846264338327950L
void usort(int a[], int n)
{
    int i,j;

    for(i=0;i<n-1;i++){
        for(j=n-1;j>i;j--){
            if(a[j-1]>a[j]){
 				      int tmp=a[i];
              a[i]=a[j];
              a[j]=tmp;
            }
        }
    }
}
int main(){
    int n,i;
    scanf("%d",&n);
    long int a[n];
    rep(i,n) scanf("%ld",&a[i]);
    usort(a,n);
    int cnt=0;
    rep(i,n-1) if(a[i]==a[i+1]) cnt++;
    if(cnt!=0) printf("NO");
    else printf("YES");
    return 0;
}