#include <algorithm>
#include <array>
#include <cstdio>
#include <cstdlib>
#include <cctype>
#include <ostream>
#include<complex>
#include <cmath>
#include <iostream>
#include <stack>
#include <fstream>
#include <queue>
#include <list>
#include <map>
#include <numeric>
#include <set>
#include <sstream>
#include <string>
#include <vector>
#include <string>
using namespace std;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;

double x,y,a,b;


double ans;
bool func(double k)
{ 
    double n = a/(a+b);
    double m = b/(a+b);
    double aa = n * k;
    double bb = m * k;
    return x > aa && y > bb;
}

int main()
{ 
    cin >> a >> b >> x >> y;

    double mid;
    double low = -100;
    double hi = 3000;
    while(hi - low > 0.00000001)
    {
        mid = (hi + low)/2;
        if(func(mid))
        {
            low = mid;
        }
        else
        {
            hi = mid;
        }
    }
    cout << low << endl;
    return 0;
}