import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        double a = input.nextDouble();
        double b = input.nextDouble();
        double h = input.nextDouble();
        double m = input.nextDouble();

        double radian = Math.PI*2*(h/12.0 + (m/60.0)/12.0 - m / 60.0);

        double rsq = (a*a+b*b) - (2*a*b)*Math.cos(radian);

        System.out.println(Math.sqrt(rsq));

    }
}
/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