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"
  "os"
  "bufio"
  "strconv"
  "sort"
)

var sc = bufio.NewScanner(os.Stdin)

func nextStr() string {
	sc.Scan()
	return sc.Text()
}

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

func main() {
  sc.Split(bufio.ScanWords)
  n := nextInt()
  a := make([]int, n)
  for i := range a {
    a[i] = nextInt()
  }
  
 //整数列をソートしてから隣接する要素を比較
  sort.Sort(sort.IntSlice(a))
  res := "YES"
  for i := 1; i < n; i++ {
    if a[i-1] == a[i] {
      res = "NO"
      break
    }
  }
  fmt.Println(res)
}