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>
int cmpfunc (const void * a, const void * b) {
  return ( *(int*)a - *(int*)b );
}
int main(){
  int N, A[200001];
  scanf("%d", &N);
  for(int i=0; i<N; i++){
    scanf("%d", &A[i]);
  }
  
  qsort(A, N, sizeof(int), cmpfunc);
  for(int i=0; i<N-1; i++){
    if(A[i]==A[i+1]){
      printf("NO");
      return 0;
    }
  }
  
  printf("YES");
  return 0;
}