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<string.h>
int main(void){
   int N,flag=0;
   long A[200001];
   scanf("%d",&N);
   for(int i=0;i<N;i++){
      scanf("%ld",&A[i]);
   }
   for(int i=0;i<N;i++){
      for(int k=i+1;k<N;k++){
         if(A[i]==A[k]){
            flag=1;
            break;
         }
      }
      if(flag==1){
         break;
      }
   }
   if(flag==1){
      printf("NO");
   }else{
      printf("YES");
   }
   return 0;
}