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 <string.h>
#include <math.h>
#include <stdlib.h>
#define BUFSIZE 200000
int n;
int hoge[BUFSIZE]={0};
int compare_int(const void *a, const void *b)
{
    return *(int*)a - *(int*)b;
}
void survey(int A){
    if(A==n-1){
        printf("YES");
        exit(0);
     }    
    if(hoge[A]==hoge[A+1]){
        printf("NO");
        exit(0);
    }
    survey(A+1);    
}
int main(void){
    scanf("%d",&n);
for(int i=0;i<n;i++){
    scanf("%d",&hoge[i]);
    }
    qsort(hoge,n,sizeof(int),compare_int);
    survey(0);
 }