//set many funcs template
//Ver.20180709
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<stdbool.h>
#include<time.h>
#define inf 1072114514
#define llinf 4154118101919364364
#define mod 1000000007
#define pi 3.1415926535897932384
#define bas 1000003

int max(int a,int b){if(a>b){return a;}return b;}
int min(int a,int b){if(a<b){return a;}return b;}
int zt(int a,int b){return max(a,b)-min(a,b);}
int round(int a,int b){if((a%b)*2 >= b){return (a/b)+1;}return a/b;}
int ceil(int a,int b){if(a%b==0){return a/b;}return (a/b)+1;}
int gcd(int a,int b){int c;while(b!=0){c=a%b;a=b;b=c;}return a;}
int lcm(int a,int b){int c=gcd(a,b);a/=c;return a*b;}
int nCr(int a,int b){int i,r=1;for(i=1;i<=b;i++){r*=(a+1-i);r/=i;}return r;}
int nHr(int a,int b){return nCr(a+b-1,b);}
int fact(int a){int i,r=1;for(i=1;i<=a;i++){r*=i;}return r;}
int pow(int a,int b){int i,r=1;for(i=1;i<=b;i++){r*=a;}return r;}
int dsum(int x){int r=0;while(x){r+=(x%10);x/=10;}return r;}
int dsumb(int x,int b){int r=0;while(x){r+=(x%b);x/=b;}return r;}
int sankaku(int x){return ((1+x)*x)/2;}
long long llmax(long long a,long long b){if(a>b){return a;}return b;}
long long llmin(long long a,long long b){if(a<b){return a;}return b;}
long long llzt(long long a,long long b){return llmax(a,b)-llmin(a,b);}
long long llround(long long a,long long b){if((a%b)*2 >= b){return (a/b)+1;}return a/b;}
long long llceil(long long a,long long b){if(a%b==0){return a/b;}return (a/b)+1;}
long long llgcd(long long a,long long b){long long c;while(b!=0){c=a%b;a=b;b=c;}return a;}
long long lllcm(long long a,long long b){long long c=llgcd(a,b);a/=c;return a*b;}
long long llnCr(long long a,long long b){long long i,r=1;for(i=1;i<=b;i++){r*=(a+1-i);r/=i;}return r;}
long long llnHr(long long a,long long b){return llnCr(a+b-1,b);}
long long llfact(long long a){long long i,r=1;for(i=1;i<=a;i++){r*=i;}return r;}
long long llpow(long long a,long long b){long long i,r=1;for(i=1;i<=b;i++){r*=a;}return r;}
long long lldsum(long long x){long long r=0;while(x){r+=(x%10);x/=10;}return r;}
long long lldsumb(long long x,long long b){long long r=0;while(x){r+=(x%b);x/=b;}return r;}
long long llsankaku(long long x){return ((1+x)*x)/2;}
double dbmax(double a,double b){if(a>b){return a;}return b;}
double dbmin(double a,double b){if(a<b){return a;}return b;}
double dbzt(double a,double b){return dbmax(a,b)-dbmin(a,b);}
int sortfncsj(const void *a,const void *b){if(*(int *)a>*(int *)b){return 1;}if(*(int *)a==*(int *)b){return 0;}return -1;}
int sortfnckj(const void *a,const void *b){if(*(int *)a<*(int *)b){return 1;}if(*(int *)a==*(int *)b){return 0;}return -1;}
int llsortfncsj(const void *a,const void *b){if(*(long long *)a>*(long long *)b){return 1;}if(*(long long *)a==*(long long *)b){return 0;}return -1;}
int llsortfnckj(const void *a,const void *b){if(*(long long *)a<*(long long *)b){return 1;}if(*(long long *)a==*(long long *)b){return 0;}return -1;}
int dbsortfncsj(const void *a,const void *b){if(*(double *)a>*(double *)b){return 1;}if(*(double *)a==*(double *)b){return 0;}return -1;}
int dbsortfnckj(const void *a,const void *b){if(*(double *)a<*(double *)b){return 1;}if(*(double *)a==*(double *)b){return 0;}return -1;}
int strsortfncsj(const void *a,const void *b){return strcmp((char *)a,(char *)b);}
int strsortfnckj(const void *a,const void *b){return strcmp((char *)b,(char *)a);}

void shuffledget(int x[],int n){
    srand(time(0));
    int i,b[524288],p,c;
    for(i=0;i<n;i++){
        b[i]=i;
    }
    for(i=n;i>=1;i--){
        p=rand()%i;
        c=b[i-1];b[i-1]=b[p];b[p]=c;
    }
    for(i=0;i<n;i++){
        scanf("%d",&x[b[i]]);
    }
}

typedef struct{
    char str[32];
    long long val;
}data;

data hmap[1048576];

void hinit(){
    long long i;
    for(i=0;i<bas;i++){
        strcpy(hmap[i].str,"");
        hmap[i].val=0;
    }
}

long long chash(char s[]){
    long long l,i,r=0,k;
    l=strlen(s);
    k=1;
    for(i=0;i<l;i++){
        r+=(k*s[i]);r%=bas;
        k*=128;k%=bas;
    }
    return r;
}

long long search(char s[]){
    long long h,p;
    h=chash(s);
    p=h;
    while(1){
        if(strcmp(hmap[p].str,s)==0){return p;}
        if(strlen(hmap[p].str)==0){return -1;}
        p++;p%=bas;
        if(p==h){return -1;}
    }
}

void add(char s[]){
    long long h,p;
    h=search(s);
    if(h!=-1){hmap[h].val++;return;}
    h=chash(s);
    p=h;
    while(1){
        if(strlen(hmap[p].str)==0){
            strcpy(hmap[p].str,s);
            hmap[p].val++;
            return;
        }
        p++;p%=bas;
        if(p==h){return;}
    }
}

int main(void){
    hinit();
    long long p,i,j,n,m,k,a[524288],b,c,w,r=0,l,t;
    long long mem[1048576]={0};
    double d;
    char s[524288],x[32],y[32],z[32];
    scanf("%lld%s",&n,s);
    //l=strlen(s);
    for(i=0;i<n;i++){x[i]=s[i];}
    for(i=0;i<n;i++){y[i]=s[2*n-1-i];}
    k=llpow(2,n);
    for(i=0;i<k;i++){
        p=0;
        t=i;
        for(j=0;j<n;j++){
            if(t%2==0){z[p]=x[j];p++;}
            t/=2;
        }
        z[p]='+';p++;t=i;
        for(j=0;j<n;j++){
            if(t%2==1){z[p]=x[j];p++;}
            t/=2;
        }
        z[p]=0;p++;
        //printf("%s\n",z);
        add(z);
    }
    for(i=0;i<bas;i++){
        mem[i]=hmap[i].val;
        hmap[i].val=0;
    }
    for(i=0;i<k;i++){
        p=0;
        t=i;
        for(j=0;j<n;j++){
            if(t%2==0){z[p]=y[j];p++;}
            t/=2;
        }
        z[p]='+';p++;t=i;
        for(j=0;j<n;j++){
            if(t%2==1){z[p]=y[j];p++;}
            t/=2;
        }
        z[p]=0;p++;
        //printf("%s\n",z);
        add(z);
    }
    for(i=0;i<bas;i++){
        r+=(mem[i]*hmap[i].val);
    }
    printf("%lld\n",r);
    return 0;
}

Measured memory_bytes: 49664