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)

fn main() {
    let mut n = String::new();
    std::io::stdin().read_line(&mut n).unwrap();
    // let n: i32 = n.trim().parse().unwrap();

    let mut line = String::new();
    std::io::stdin().read_line(&mut line).expect("error!");
    let v: Vec<i32> = line.split_whitespace().map(|s| s.parse().expect("err")).collect();
    let mut v_s: Vec<i32> = v.clone();
    v_s.sort();

    let mut counter: i32 = 0;
    for (&i, &j) in v.iter().zip(v_s.iter()) {
        if i != j {
            counter += 1;
        }
    }

    if counter == 0 || counter == 2 {
        println!("YES");
    } else {
        println!("NO");
    }
}