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 JavaScript (node.js v5.12) (judge verdict: Accepted)

'use strict'


function Main(input) {
  input = input.trim().split('\n')
  const N = parseInt(input[0])

  const A = input[1].split(' ').map(s => parseInt(s))

  let dp = {}
  for(let i = 0; i < N; ++i) {
    if(!dp[A[i]]) dp[A[i]] = 0
    if(dp[A[i]] > 0) {
      console.log('NO')
      return
    }
    dp[A[i]] += 1
  }

  console.log('YES')
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));