import java.util.Scanner;
public class Main {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        double a = scanner.nextDouble();
        double b = scanner.nextDouble();
        int h = scanner.nextInt();
        int m = scanner.nextInt();

//        角度を求める
        double angle = (h * 30.0 + m * 0.5) - ( m * 6.0 );
        double angles = Math.abs(angle);

        double before = Math.sqrt(Math.pow(a,2) + Math.pow(b,2)
                                    - (2.0 * a * b * Math.cos(Math.toRadians(angles))));
        System.out.println(before);

        scanner.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