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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include<algorithm>
#include<vector>
#include <iostream>
using namespace std;
int main(void){
    // Your code here!
    int N;
    cin >> N;
    vector<int> P;
    int PP[N];
    for(int i = 0 ; i< N;i++){
        cin >> PP[i];
        P.push_back(PP[i]);
    }
    sort(P.begin(),P.end());
    int cont = 0;
    string ans ="YES";
    for(int i = 0; i < N ;i++){
           if(P[i]!=PP[i])cont++;
            if(cont >2)ans ="NO";
    }
    
    cout << ans << endl;
}