#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n,m;
    while(scanf("%d%d",&n,&m)==2)
    {
        double ans=0.0;
        for(int i=1;i<n;i++){
            double pos = (double) i / n * (n+m);
            ans += fabs(pos - floor(pos + 0.5)) / (n+m);
        }
        printf("%.4lf\n",ans*10000);
    }
    return 0;
}