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

  int f=0;
  for(int i=0;i<n;i++){
    for(int j=i+1;j<n;j++){
      if(a[i]==a[j]){
	f=1; break;}}}

  if(f==0) printf("YES\n");
  else printf("NO\n");

  return 0;
}