import java.util.Scanner;

public class yukicoder_236 {
	public static void main(String[] args) {
		Scanner stdIn = new Scanner(System.in);
		
		int a = stdIn.nextInt();
		int b = stdIn.nextInt();
		int x = stdIn.nextInt();
		int y = stdIn.nextInt();
		
		double ax = (double)x / a;
		double by = (double)y / b;
		
		if (ax >= by) {
			System.out.println((a + b) * by);
		} else {
			System.out.println((a + b) * ax);
		}
	}
}