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: Wrong Answer)

#include <bits/stdc++.h>
#define rep(i, n) for(int i=0;i<(n); i++)
#define sz(x) int(x.size())
using namespace std;

int main(){
    int n;
    cin >> n;
    int temp;
    bool b;
    vector<int> nn(n);
    vector<int> co(n);
    rep(i, n){ cin >> nn.at(i); co[i] = nn[i];}

    sort(co.begin(), co.end());

    rep(i, sz(nn)){
        if(nn[i]==co[i])continue;
        if(!b){
        
        temp = nn[i];
        nn.erase(nn.begin() + i);
        b=true;
        }
        else{
            if(nn[i]!=co[i]){
                nn.insert(nn.begin()+i, temp);
                break;
            }
        }
    }

    b=false;
    rep(i, n)if(nn[i]!=co[i])b=true;

    if(b){
        cout << "NO" << endl;
    }else{
        cout << "YES" << endl;

    }
    return 0;
}