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: Wrong Answer)

#include<stdio.h>
#include<string.h>
int main(void)
{
  
  int i,j,N;
  int flag=1;
  int A[200001];
    scanf("%d\n",&N);
  for(i=0;i<N;i++){
    scanf("%d",&A[i]);
  }
  i=-1;
  while(flag!=0 && i<N){
     i=i+2;
    for(j=i;j<N-1;j++){
      if(A[i]==A[j+1] || A[N-1-i]==A[N-1-(j+1)]){
        flag=0;
        break;
      }
    }
  }
  if(flag==0)
    printf("NO");
  if(flag==1)
    printf("YES");
    return 0;
}