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<stdlib.h>
#include<math.h>
#include<string.h>

int main(){
    long long int N;
    scanf("%lld",&N);
    long long int A[N+1];
    long long int i,j,s=0,count=0;
    for(i=0;i<N;i++){
        scanf("%lld",&A[i]);
    }

    for(i=0;i<N;i++){
        for(j=i+1;j<N;j++){
            if(A[i]!=A[j]){
                count +=1;
            }
        }
    }
    for(i=1;i<N;i++){
        s = s+i; 
    }
    if(s==count){
        printf("YES");
    }
    else{
        printf("NO");
    }

    return 0;
}