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 Go (1.6) (judge verdict: Accepted)

package main

import "fmt"

func main() {
	var N int
	fmt.Scan(&N)

	a := make([]int, N)
	for i := 0; i < N; i++ {
		fmt.Scan(&a[i])
	}

	m := make(map[int]int)

	for _, v := range a {
		m[v]++
	}

	var isNO bool
	for _, v := range m {
		if v > 1 {
			fmt.Println("NO")
			isNO = true
			break
		}
	}
	if !isNO {
		fmt.Println("YES")
	}
}