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: Runtime Error)

package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

var stdin = bufio.NewScanner(os.Stdin)

func main() {
	stdin.Split(bufio.ScanWords)
	var N int
	var A []int
	var B int

	N = nextInt()
	for i:=0;i<N-1;i++ {
		B = nextInt()
		for j := range A {
			if B == A[j] {
				fmt.Println("NO")
				os.Exit(0)
			}
		}
		A = append(A, nextInt())
	}
	fmt.Println("YES")
}

func nextInt() int {
	stdin.Scan()
	i, err := strconv.Atoi(stdin.Text())
	if err != nil {
		panic(err)
	}
	return i
}