import java.util.Scanner;



public class Main {


	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int a = Integer.parseInt(sc.next());
		int b = Integer.parseInt(sc.next());
		int h = Integer.parseInt(sc.next());
		int m = Integer.parseInt(sc.next());

		double l = m * 6;
		double s = (h * 60 + m) * 0.5;
		double kakudo = s - l;
		double result = Math.cos(Math.toRadians(kakudo));
		double rsq = (a * a) + (b * b) - (2 * a * b * result);
		System.out.println(Math.sqrt(rsq));


	}
}

/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