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)

// Created by code_sm
//
#include<bits/stdc++.h>
using namespace std;
//#include <ext/pb_ds/assoc_container.hpp> 
//using namespace __gnu_pbds;
//typedef tree<int,null_type,less<int>,rb_tree_tag, tree_order_statistics_node_update> pseudo_set;
#define ll long long
#define vi vector<int>
#define si set<int> 
#define mii map<int,int>
#define pb push_back
#define pf push_front
#define pii pair<int,int>
#define extract_word(s)  stringstream str(s); while(str>>word)
#define fastio ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define SET(s) cout<<fixed<<setprecision(s)
#define chotu 1000000007
#define set0(a) memset(a,0,sizeof(a))
#define endl "\n"
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define lower_string(s) transform(all(s),s.begin(),::tolower())
#define upper_string(s) transform(all(s),s.begin(),::toupper())
#define size(s) s.size()
template<class T> bool umin(T &a, T b) { return a > b ? (a = b, true) : false; }
template<class T> bool umax(T &a, T b) { return a < b ? (a = b, true) : false; }
template<typename T,typename U>
bool compare(T x,U y){return(abs(x-y)<=1e-9);}
void solve()
{
fastio
	int n;
	cin>>n;
	int p[n];
	for(auto &x:p)
		cin>>x;
	int des[n];
	for(int i=0;i<n;i++)
		des[i]=i+1;
	int c=0;
	for(int i=0;i<n;i++)
	{
		if(p[i]!=des[i])
		{
c++;
		}
	}
	if(c>2)
		cout<<"NO";
	else
		cout<<"YES";
}
int main()
{
//code
	
fastio	
int t;
t=1;
while(t--)
{
	solve();
	cout<<endl;
}
}