#include <bits/stdc++.h>
using namespace std;
map<pair<string, string>,int> g;
int n;
char s[100005];
long long z;
int main(){
	cin>>n;
	scanf("%s",s);
	for(int i=0;i<1<<n;i++){
		string a,b;
		for (int j=0;j<n;j++){
			if ((i>>j)&1)a+=s[j];
			else b+=s[j];
		}
		g[{a, b}]++;
	}
	for(int i=0;i<1<<n;i++) {
		string a,b;
		for (int j=0;j<n;j++) {
			if((i>>j)&1)a+=s[2*n-1-j];
			else b+=s[2*n-1-j];
		}
		z+=g[{a,b}];
	}
	cout<<z<<endl;
	return 0;
}
### Prompt

Your challenge is to write a cpp solution to the following problem:

You are given a string S of length 2N consisting of lowercase English letters.

There are 2^{2N} ways to color each character in S red or blue. Among these ways, how many satisfy the following condition?

* The string obtained by reading the characters painted red from left to right is equal to the string obtained by reading the characters painted blue from right to left.

Constraints

* 1 \leq N \leq 18
* The length of S is 2N.
* S consists of lowercase English letters.

Input

Input is given from Standard Input in the following format:


N
S


Output

Print the number of ways to paint the string that satisfy the condition.

Examples

Input

4
cabaacba


Output

4


Input

11
mippiisssisssiipsspiim


Output

504


Input

4
abcdefgh


Output

0


Input

18
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa


Output

9075135300

### Response

```cpp
#include <bits/stdc++.h>
using namespace std;
map<pair<string, string>,int> g;
int n;
char s[100005];
long long z;
int main(){
	cin>>n;
	scanf("%s",s);
	for(int i=0;i<1<<n;i++){
		string a,b;
		for (int j=0;j<n;j++){
			if ((i>>j)&1)a+=s[j];
			else b+=s[j];
		}
		g[{a, b}]++;
	}
	for(int i=0;i<1<<n;i++) {
		string a,b;
		for (int j=0;j<n;j++) {
			if((i>>j)&1)a+=s[2*n-1-j];
			else b+=s[2*n-1-j];
		}
		z+=g[{a,b}];
	}
	cout<<z<<endl;
	return 0;
}
```