import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.Scanner;
import java.util.Set;
import java.util.TreeSet;

public class Main {
	
	
	
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		final int A = sc.nextInt();
		final int B = sc.nextInt();
		final int X = sc.nextInt();
		final int Y = sc.nextInt();
		
		final int left  = Y * A;
		final int right = X * B;
		
		//System.out.println(left + " " + right);
		
		if(left >= right){
			System.out.printf("%.8f\n", X + Y - (left - right) / (double)(A));
		}else{
			System.out.printf("%.8f\n", X + Y - (right - left) / (double)(B));
		}
	}
	
	
}