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: Runtime Error)

use std::io;
fn main() {
    let mut l1 = String::new();
    let mut l2 = String::new();

    io::stdin().read_line(&mut l1).unwrap();
    io::stdin().read_line(&mut l2).unwrap();

    let p_str: Vec<&str> = l2.trim().split(" ").collect();
    let mut p: Vec<i32> = [].to_vec();
    let n: i32 = l1.trim().parse().unwrap();

    for num in p_str.iter() {
        let num = num.parse::<i32>().unwrap();
        p.push(num);
    }

    let mut p_asc = p.clone();
    p_asc.sort();

    if p_asc == p {
        println!("YES");
        return;
    }

    let foo = p.remove((n - 1) as usize);

    for (i, _) in p.iter().enumerate() {
        let mut pc = p.clone();
        let bar = pc.remove(i);
        pc.insert((n - 2) as usize, bar);
        pc.insert(i as usize, foo);

        if pc == p_asc {
            println!("YES");
            return;
        }

        let mut pcc = p.clone();
        let barc = pcc.remove(i);
        pcc.insert((n - 1) as usize, foo);
        pcc.insert(i as usize, barc);

        if pcc == p_asc {
            println!("YES");
            return;
        }

        // println!("pc:  {:?} {:?}", pc, p_asc);
        // println!("pcc: {:?} {:?}", pcc, p_asc);
    }

    println!("NO");
}