import java.util.Scanner;
class Main{
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        double a = scan.nextDouble();
        double b = scan.nextDouble();
        double h = scan.nextDouble();
        double m = scan.nextDouble();
        double naga = m * 360 / 60;
        double miji = (h * 60 + m) * 360 / (12 * 60);
        double kaku = miji - naga;
        double result = Math.sqrt(a*a + b*b - 2*a*b* Math.cos(Math.toRadians(kaku)));
        System.out.println(result);

    }
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz