import java.util.Scanner;

/**
 * No.236 鴛鴦茶
 */
public class OshidoriTea {

	public static void main(String[] args) {

		// 標準入力から読み込む際に、Scannerオブジェクトを使う。
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int x = sc.nextInt();
        int y = sc.nextInt();

        int l = a * y;
        int r = b * x;
        
        double d = 0d;
        if (l >= r) {
        	d = x + y - (l - r) / (double) a;
        } else {
        	d = x + y - (r - l) / (double) b;
        }
    	System.out.printf("%.8f\n",d);
	}

}