#include <bits/stdc++.h>
using namespace std;
map<pair<string, string>, int> g;
int n;
string s;
long long z;
int main() {
	cin >> n;
	cin >> 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

Create a solution in cpp for 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;
string s;
long long z;
int main() {
	cin >> n;
	cin >> 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;
}
```