import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        Integer a = scanner.nextInt();
        Integer b = scanner.nextInt();
        Integer h = scanner.nextInt();
        Integer m = scanner.nextInt();

        double result;

        double rad = Math.PI * 2 * ((double)h / 12 + ((double)m / 60) / 12 - (double)m / 60);

        result = Math.sqrt(Math.pow(a,2) + Math.pow(b,2) - 2*a*b*Math.cos(rad));

        System.out.printf("%.20f",result);
    }
}

/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