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.Arrays;
import java.util.Scanner;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);

    int N = sc.nextInt();
    int[] A = new int[N];
    int count = 0;

    for (int i = 0; i < N; i++) {
      A[i] = sc.nextInt();
    }

    Arrays.sort(A);

    if (N == 2) {
      for (int i = 0; i < N - 1; i++)
        if (A[i] == A[i + 1]) {
          count++;
        }
    } else {
      for (int i = 0; i < N - 2; i++) {
        if (A[i] == A[i + 1]) {
          count++;
        }
      }
    }


      if (0 == count) {
        System.out.println("Yes");
      } else if (0 < count) {
        System.out.println("No");
      }
    }
  }