import java.util.*;

public class Main{
    public static void main(String[] args){
        Scanner scan = new Scanner(System.in);
        int a = scan.nextInt();
        int b = scan.nextInt();
        int h = scan.nextInt();
        int m = scan.nextInt();
        double angle = h * 30 - m * 5.5;
        angle = Math.abs(angle > 180 ? 360 - angle : angle);
        System.out.println(Math.sqrt(a * a + b * b - 2 * a * b * Math.cos(Math.toRadians(angle))));
        scan.close();
    }
}
/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