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 C++ (Clang 10.0.0) (judge verdict: Wrong Answer)

#include <iostream>
#include <stdlib.h>

using namespace std;

int main()
{
    int arr [50];
    int n, flag = 1;

    cin >> n;

    if (n<2 || n >50) {
        cout << "Number of elements should be between 2-100" << endl;
        exit (0);
    }

    for (int i=0; i<n; i++) {
        cin >> arr [i];
    }

    for (int i=0; i<n-1; i++) {
        if (!(arr[i] < arr [i+1])) {
            flag = 0;
            break;
        }
    }

    if ((flag == 1) || (arr[0]>arr[n-2] && arr[n-1] < arr[1])) {
            cout << "YES" << endl;
        }
    else {
            cout << "NO" << endl;
    }

    return 0;
}