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 (Clang 3.8.0) (judge verdict: Time Limit Exceeded)

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

int main(void) {
  int n;
  int a[200000];
  char str_n[7];
  char str_ai[11];
  
  int l;
  int i, j;

  scanf("%s", str_n);
  n = atoi(str_n);
  
  for(i=0; i<n; i++) {
    scanf("%s", str_ai);
    a[i] = atoi(str_ai);
  }
  
  for(i=0; i<n; i++) {
    for(j=i+1; j<n; j++) {
      if(a[i] == a[j]) {
        printf("NO\n");
        return 0;
      }
    }
  }
  
  printf("YES\n");
  
  return 0;

}