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 tmp1 = sc.nextDouble();
		double tmp2 = sc.nextDouble();
		double h = tmp1 / 6. * Math.PI + tmp2 / 30. * Math.PI / 12.;
		double m = tmp2 / 30. * Math.PI + tmp1 / 6. * Math.PI * 12.;
		double rad = h - m;
		// System.out.println(rad / Math.PI / 2. * 360.);
		double res = Math.sqrt(Math.pow(a, 2) + Math.pow(b, 2) - (2. * a * b * Math.cos(rad)));
		System.out.println(res);
	}

}
/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