#include <fstream>
#include <cstdlib>
#include <iomanip>
using namespace std;

ifstream f("minesweeper.in");
ofstream g("minesweeper.out");

int n,m,v[24],k,x,i,z;
double s;

int main () {
    f >> n >> m;
    n=n*m;
    s=2*n;
    k=1;
    for (i=1;i<=4000;i++) {
        k++;
        s+=2*i;
    }
    s=(double)s/k;
    g << fixed;
    g << setprecision(6) << s;
    f.close();g.close();
    return 0;
}