import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int A = sc.nextInt();
        int B = sc.nextInt();
        double H = sc.nextDouble();
        double M = sc.nextDouble();
        sc.close();

        double Hx = A * Math.sin(Math.toRadians(360 * (H + M / 60) / 12));
        double Hy = A * Math.cos(Math.toRadians(360 * (H + M / 60) / 12));

        double Mx = B * Math.sin(Math.toRadians(360 * M / 60));
        double My = B * Math.cos(Math.toRadians(360 * M / 60));

        double x = (Hx - Mx);
        double y = (Hy - My);

        System.out.println(Math.sqrt(Math.pow(x, 2) + Math.pow(y, 2)));
    }
}
/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