Problem:
Score : 200 points

Problem Statement

We have a sequence p = {p_1,\ p_2,\ ...,\ p_N} which is a permutation of {1,\ 2,\ ...,\ N}.

You can perform the following operation at most once: choose integers i and j (1 \leq i < j \leq N), and swap p_i and p_j. Note that you can also choose not to perform it.

Print YES if you can sort p in ascending order in this way, and NO otherwise.

Constraints

All values in input are integers.

2 \leq N \leq 50

p is a permutation of {1,\ 2,\ ...,\ N}.

Input

Input is given from Standard Input in the following format:

N
p_1 p_2 ... p_N

Output

Print YES if you can sort p in ascending order in the way stated in the problem statement, and NO otherwise.

Sample Input 1

5
5 2 3 4 1

Sample Output 1

YES

You can sort p in ascending order by swapping p_1 and p_5.

Sample Input 2

5
2 4 3 5 1

Sample Output 2

NO

In this case, swapping any two elements does not sort p in ascending order.

Sample Input 3

7
1 2 3 4 5 6 7

Sample Output 3

YES

p is already sorted in ascending order, so no operation is needed.

Solution in Go (1.6) (judge verdict: Accepted)

package main
import "fmt"

func main() {
  var n int
  fmt.Scan(&n)
  flag := 1
  
  l := make([]int, n)
  for i:=0; i<n; i++ {
    fmt.Scan(&l[i])
  }
  
  var temp int
  for i:=0; i<n; i++ {
    if l[i] != i+1 {
      for j:=0; j<n; j++ {
        if l[j] == i+1 {
          temp = l[i]
          l[i] = l[j]
          l[j] = temp
        }
      }
      break
    }
  }
  for i:=0; i<n; i++ {
    if l[i] != i+1 {
      flag = 0
    }
  }
  if flag == 1 {
    fmt.Println("YES")
  } else {
    fmt.Println("NO")
  }
}