#define _USE_MATH_DEFINES	//M_PI(π),M_SQRT2(√2)
#include <iostream>			//std::cout, std::cin
#include <string>			//std::string,std::to_string(C++11)
#include <vector>			//std::vector
#include <valarray>			//std::valarray
#include <algorithm>		//std::sort
#include <time.h>			//localtime_s
#include <cstdlib>			//abs
#include <cmath>			//abs,std::pow,sqrt,sin,cos,round,floor,ceil
#include <fstream>			//std::ifstream,std::ofstream
#include <iomanip>			//std::setprecision,std::setw,std::setfill
#include <random>			//std::random(C++11)
#include <numeric>			//std::accumulate

int main(void) {

	//test用
	//std::ifstream in("test.txt");
	//std::cin.rdbuf(in.rdbuf());

	//const unsigned int MODULO = 1000000007;	//MODULO 10^9+7用

	double A, B, X, Y;
	std::cin >> A >> B >> X >> Y;

	double i = 1, ans = 0;
	if (A < B) {
		while (i <= Y && i*A / B <= X) {
			i++;
		}
		ans = (i - 1) + ((i - 1)*A / B);
	}
	else {
		while (i <= X && i*B / A <= Y) {
			i++;
		}
		ans = (i - 1) + ((i - 1)*B / A);
	}

	std::cout << std::fixed << std::setprecision(10) << ans << std::endl;


}