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 Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.util.*;

public class Main{
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    Integer a[] = new Integer[N];
    for(int i = 0; i < N; i++){
      a[i] = sc.nextInt();      
    }
    Arrays.sort(a, Comparator.naturalOrder());
    
    int judge = 0;
    
    for(int i = 1; i < N; i++){
      if(a[i-1] == a[i]){
        judge++;
      }
    }
    if(judge == 0){
      System.out.println("YES");
    }else{
      System.out.println("NO");
    }

}
}