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;
 
typedef long long ll;
typedef double D;
typedef vector<int> VI;
typedef vector<ll> VL;
typedef pair<int,int> PII;
typedef pair<ll,ll> PLL;
typedef long double ld;

#define rd(x) scanf("%d",&x)
#define rd2(x,y) scanf("%d %d",&x,&y)
#define rl(x) scanf("%lld",&x)
#define rl2(x,y) scanf("%lld %lld",&x,&y)
#define wd(x) printf("%d" ,x)
#define wd2(x,y) printf("%d %d",x,y)
#define wl(x) printf("%lld",x)
#define wl2(x,y) printf("%lld %lld",x,y)
#define PC(x) putchar(x)
#define GC() getchar()
#define NL printf("\n")
#define SP printf(" ")
 
#define SZ(a) (int)a.size()
#define ALL(a) a.begin(), a.end()
#define ITER(it,a) for (__typeof(a.begin()) it = a.begin(); it != a.end(); it++)
#define FILL(a,value) memset(a, value, sizeof(a))

#define F first
#define S second
#define MP make_pair
#define PB push_back

#define SPEED ios::sync_with_stdio(false); cin.tie(0); cout.tie(0)
#define fastio ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define fast_cin() ios_base::sync_with_stdio(false); cin.tie(NULL)
#define fr(i,s,e) for(int i=s;i<e;i++)
#define frl(i,s,e) for(ll i=s;i<e;i++)
#define frr(i,s,e) for(int i=s-1;i>=e;i--)
#define frv(i,a) for(int i = 0;i<(int)a.size();i++)
#define frvr(i,a) for(int i = a.size()-1;i>=0;i--)
#define tr(i,a) for(typeof(a.begin()) i = a.begin(); i != a.end();i++)

#define inf 10000000000000
#define mod 1000000007
#define maxn 100009
#define maxr 100009
int main(){
	//s(std::ios::sync_with_stdio(false); cin.tie(NULL);
	ll n;
	rl(n);
	VL arr(n),tmp;
	fr(i,0,n)
		rl(arr[i]);
	tmp=arr;
	sort(ALL(tmp));
	ll ct=0;
	fr(i,0,n)
	{
		if(arr[i]!=tmp[i])
			ct++;
	}
	if(ct<=2)
		cout<<"YES"<<endl;
	else
		cout<<"NO"<<endl;
}