import java.util.*;
 
public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        double a, b, h, m;
        a = sc.nextDouble();
        b = sc.nextDouble();
        h = sc.nextDouble();
        m = sc.nextDouble();
        double angle = Math.min(Math.abs(h * 30 + m * 0.5 - m * 6), 360 - Math.abs(h * 30 + m * 0.5 - m * 6));
        double pi = angle / 180 * Math.PI;
        System.out.println(Math.sqrt(a * a + b * b - 2 * a * b * Math.cos(pi)));
    }
}
/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