#include <bits/stdc++.h>
#define rep(i, a) for (int i = 0; i < (a); i++)
#define rep2(i, a, b) for (int i = (a); i < (b); i++)
using namespace std;
typedef long long ll;
const ll inf = 1e9;
const ll mod = 1e9 + 7;

int main() {
    double A, B, X, Y;
    cin >> A >> B >> X >> Y;

    printf("%.15f\n", min(B * X / A + X, A * Y / B + Y));
}