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)

typedef long long ll;
/*
id: sadykhzadeh -> @Azer_Sadykhzadeh
Programming Language: (C++)
*/
using namespace std;
#include <iostream>
#include <iomanip>
#include <vector>
#include <algorithm>
#include <iterator>
#define pb push_back
int main(){
    ll N; cin >> N; ll k = N;
    vector <ll> a, b;
    ll cnt(0);
    for(ll i = 0; i< N; i++){
        ll temp; cin >> temp; a.pb(temp); b.pb(temp);
    }
    if(is_sorted(a.begin(), a.end())) return cout << "YES" << endl, 0;
  //  if(is_sorted())
    for(ll i = 0; i < N - 1; i++){
        for(ll j = i + 1; j < N; j++){
            if(a[i] > a[j]){
                swap(a[i], a[j]);
                //cnt++;
            }
        }
    }
    for(ll i = 0; i < N; i++){
        if(a[i] != b[i]) cnt++;
    }
    if(cnt == 2) return cout << "YES" << endl, 0;
    else cout << "NO" << endl, 0;
}