#include <iostream>
#include <iomanip>

using ldouble = long double;

void solve() {
    ldouble a, b, x, y;
    std::cin >> a >> b >> x >> y;

    std::cout << std::fixed << std::setprecision(10)
              << std::min(x / a, y / b) * (a + b) << std::endl;
}

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    solve();

    return 0;
}