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

Solution (in PYTHON3):

Solution:
import sys
def I(): return int(sys.stdin.readline().rstrip())
def LS2(): return list(sys.stdin.readline().rstrip())  #空白なし


N = I()
S = LS2()

from collections import defaultdict

d_left = defaultdict(int)
d_right = defaultdict(int)

# 半分全列挙

for i in range(2**N):
    left_red = ''
    left_blue = ''
    right_red = ''
    right_blue = ''
    for j in range(N):
        if (i >> j) & 1:
            left_red += S[j]
        else:
            left_blue += S[j]
    for j in range(2*N-1,N-1,-1):
        if (i >> (j-N)) & 1:
            right_red += S[j]
        else:
            right_blue += S[j]
    d_left[(left_red,left_blue)] += 1
    d_right[(right_red,right_blue)] += 1

ans = 0
for key in d_left.keys():
    ans += d_left[key]*d_right[key]

print(ans)