#include <stdio.h>

const int n = 25;
double u[n*n];

int main ()
{
    for (int i=0; i<n*n; i++)
        u[i] = 1.0;
    
    for (int i=0; i<100000000/(n*n); i++)
        for (int pos1=n; pos1<(n-1)*n; pos1+=n)
            for (int pos2=pos1+1; pos2<pos1+n-1; pos2++)
                u[pos2] += 8.0/3.0 * u[pos2] - 1.0/3.0 *
                    (u[pos2-n-1]+u[pos2-1]+u[pos2+n-1]+u[pos2-n]+
                     u[pos2+n]+u[pos2-n+1]+u[pos2+1]+u[pos2+n+1]);
    printf("%f", u[n+1]);
    
    return 0;
}