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 Rust (1.15.1) (judge verdict: Accepted)

use std::io;

fn work() -> &'static str {
  let mut line = String::new();
  io::stdin().read_line(&mut line).expect("");
  line = "".to_string();
  io::stdin().read_line(&mut line).expect("");
  let v: Vec<i32> = line.split_whitespace().map(|x| x.parse::<i32>().expect("")).collect();

  let mut i = 0;
  let mut c = 0;
  for x in v {
    i = i + 1;
    if x != i {
      c = c + 1;
    }
  }

  if c == 0 || c == 2 {
    return "YES";
  }
  return "NO";
}

fn main() {
  print!("{}\n", work());
}