import java.util.Scanner;
import java.lang.Math;

public class Main {
		public static void main (String args[]) throws Exception{
		Scanner scan = new Scanner(System.in);
		double  a = scan.nextDouble();
		double  b = scan.nextDouble();
		double  h = scan.nextDouble();
		double  m = scan.nextDouble();
		double ans = 0;
		h = h * 30 + m * 0.5;
		m = m * 6;
		double angle = Math.abs(h - m);
		ans = a*a + b*b -2*a*b*Math.cos(angle/180*Math.PI);
		System.out.println(Math.sqrt(ans));
	}
}
/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