import std.algorithm, std.array, std.container, std.range, std.bitmanip;
import std.numeric, std.math, std.bigint, std.random, core.bitop;
import std.string, std.regex, std.conv, std.stdio, std.typecons;

void main()
{
  auto rd = readln.split.map!(to!int);
  auto a = rd[0], b = rd[1], x = rd[2], y = rd[3];

  auto x2 = y.to!real / b * a;
  auto y2 = x.to!real / a * b;

  writefln("%.7f", min(x, x2) + min(y, y2));
}