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.HashSet;
import java.util.Scanner;
import java.util.Set;

 class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n=in.nextInt();
        Set<Integer> s=new HashSet<>();
        boolean flag=false;
        for(int i=0;i<n;i++){
            int x=in.nextInt();
            if(s.contains(x)){
                flag=true;
                break;
            }else
                s.add(x);

        }
        if(!flag)
            System.out.println("YES");
        else
            System.out.println("NO");
    }
}