import java.util.*;

public class Main {

    public static void main(String[] args) {
        // write your code here
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        double h = sc.nextInt();
        double m = sc.nextInt();
        double theta = (h * 60 + m) / 720 - m / 60;
        theta *= Math.PI * 2;
        System.out.println(Math.sqrt(- Math.cos(theta) * 2 * a * b + a * a + b * b));
    }
}
/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