import java.util.*;
import static java.lang.System.*;
import java.math.*;

public class Main {
	static Scanner sc = new Scanner(System.in);
	public static void main(String[] args) {
		BigDecimal a = BigDecimal.valueOf(sc.nextInt());
		BigDecimal b = BigDecimal.valueOf(sc.nextInt());
		BigDecimal base = a.add(b);
		
		BigDecimal x = BigDecimal.valueOf(sc.nextInt());
		BigDecimal y = BigDecimal.valueOf(sc.nextInt());
		BigDecimal x_rate = x.divide(a,8,RoundingMode.HALF_UP);
		BigDecimal y_rate = y.divide(b,8,RoundingMode.HALF_UP);
		
		if (x_rate.compareTo(y_rate) <= 0) {out.println(base.multiply(x_rate));}
		else {out.println(base.multiply(y_rate));}
	}
}