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: Accepted)

import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        
        Scanner scanner = new Scanner(System.in);
        
        int N = scanner.nextInt();
        boolean hantei = false;
        
        Map<Integer,Integer> map = new HashMap<Integer,Integer>();
        
        for(int i=0; i<N; i++){
            
            int x = scanner.nextInt();
            if(map.containsKey(x)){
                hantei = true;
            }else{
                map.put(x,1);
            }
            
        }
        
        if(hantei){
            System.out.println("NO");
        }else{
            System.out.println("YES");
        }
        
    }
}