import java.util.Scanner;
public class Main {
 
	public static void main(String[] args) {
 
 
		double ans = 0;
		Scanner scan = new Scanner(System.in);
		int minutes_length  = scan.nextInt();
		int hour_length  = scan.nextInt();
		double hour_time  = scan.nextInt();
		double minutes_time  = scan.nextInt();
 
 
 
		double minutes_pi = Math.PI/30*minutes_time;
		double hour_pi = Math.PI/6*(hour_time+ minutes_time/60);
		double theta = Math.PI/30*(5*(hour_time+ minutes_time/60)-minutes_time);
		ans = minutes_length*minutes_length+hour_length*hour_length-2*hour_length*minutes_length*Math.cos(theta);
 
 
		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