import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner s = new Scanner(System.in);
        int A = s.nextInt();
        int B = s.nextInt();
        int H = s.nextInt();
        int M = s.nextInt();

        double Hx = A * Math.cos(Math.toRadians(90 - 30 * H - (double) M / 2));
        double Hy = A * Math.sin(Math.toRadians(90 - 30 * H - (double) M / 2));

        double Mx = B * Math.cos(Math.toRadians(90 - 6 * M));
        double My = B * Math.sin(Math.toRadians(90 - 6 * M));

        double d = Math.sqrt((Hx - Mx) * (Hx - Mx) + (Hy - My) * (Hy - My));
        System.out.print(d);
    }
}
/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