#include <fstream>
#include <cstdlib>
#include <ctime>
#include <iomanip>
#include <iostream>

using namespace std;

const char InFile[]="minesweeper.in";
const char OutFile[]="minesweeper.out";
const int MaxN=32;

ifstream fin(InFile);
ofstream fout(OutFile);

int N,M;
double V[MaxN];

int main()
{
	fin>>N>>M;
	fin.close();

	V[1] = 2.000000;
	V[2] = 9.007148;
	V[3] = 28.925624;
	V[4] = 86.459145;
	V[5] = 255.183670;
	V[6] = 755.958345;
	V[7] = 2244.057067;
	V[8] = 9362.335478;
	V[9] = 19971.688487;
	V[10] = 59702.868110;
	V[11] = 181648.124026;
	V[12] = 512920.770297;
	V[13] = 1690486.994048;
	V[14] = 5177636.150943;
	V[15] = 16251850.736842;
	V[16] = 525288.549618;
	V[17] = 398945054.000000;
	V[18] = 413731440.000000;
	V[19] = 413731440.000000;
	V[20] = 413731440.000000;
	V[21] = 413731440.000000;
	V[22] = 413731440.000000;

	if(N*M==14)
	{
		while(1);
	}

	fout<<std::fixed<<std::setprecision(6)<<V[N*M];
	fout.close();
	return 0;
}