import std.stdio,
       std.conv,
       std.string,
       std.range,
       std.math,
       std.algorithm;

void main()
{
    auto input = readln.split.to!(real[]);
    auto A = input[0], B = input[1], X = input[2], Y = input[3];

    if (A > B)
    {
        swap(A, B);
        swap(X, Y);
    }
    auto rate = A / B;
    auto few  = min(Y * rate, X);
    auto many = few / rate;
    "%.15s".writefln(few + many);
}