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<bits/stdc++.h>
#define int long long
#define x first
#define y second
#define pb push_back

#define speed ios_base::sync_with_stdio(0);cin.tie(0);
using namespace std;
signed main()
{
    speed
    int n;cin>>n;
    vector<int> inp(n);
    for(int i=0;i<n;++i){cin>>inp[i];}
    std::vector<int> tinp=inp;
    sort(tinp.begin(),tinp.end());
    int ct=0;
    for(int i=0;i<n;++i)
    {
        if(tinp[i]!=inp[i]){++ct;}
    }
    if(ct==0||ct==2){cout<<"YES";}
    else{cout<<"NO";}
}