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>
using namespace std;
int main()
{
  long long int n,i,t=0;
  cin>>n;
  long long int arr[n],brr[n];
  for(i=0;i<n;i++)
  {
    cin>>arr[i];
  }
  for(i=0;i<n;i++)
  {
    brr[i]=arr[i];
  }
  
  sort(arr,arr+n);
  for(i=0;i<n;i++)
  {
    if(arr[i]!=brr[i])
    {
      t++;
    }
  }
  /*for(i=0;i<n;i++)
  {
    cout<<arr[i];
  }
  cout<<endl;
  for(i=0;i<n;i++)
  {
    cout<<brr[i];
  }*/
  if(t==2 || t==0)cout<<"YES"<<endl;
  else cout<<"NO"<<endl;
}