#include <iostream>

using namespace std;

long double comb(long double n, long double k)
{
        long double ans = 1;
        long double lim = n - k;
        long double j = 1;
        long double q = 1;
        for(long double i = k + 1; i <= n; i++)
        {
                ans *= i;
                if(j <= lim)
                {
                        ans /= j;
                        j++;
                }
                while(ans >= 1 && q <= n)
                {
                        ans *= 0.5;
                        q++;
                }
        }
        while(j <= lim)
        {
                ans /= j;
                j++;
        }
        while(q <= n)
        {
                ans *= 0.5;
                q++;
        }
        return ans;
}

int main()
{
        int x, y;
        cin >> x >> y;
        x--;
        y--;
        long double a = comb(x + y, y);
        cout << a << "\n";
        return 0;
}
/**

**/