#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>
#include <complex>
#include <queue>
#include <set>
#include <map>
#include <iomanip>

using namespace std;

#define REP(i,a,b) for(int i=a;i<(int)b;i++)
#define rep(i,n) REP(i,0,n)

typedef long long ll;

int main() {

  int a, b, x, y; cin >> a >> b >> x >> y;
  cout << setprecision(10) << (a+b)*min((double)x/a, (double)y/b) << endl;

  return 0;
}