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();
	int h=sc.nextInt();
	int m=sc.nextInt();
	double angle = Math.abs(h*30+m*0.5-m*6);
	double result = Math.cos(Math.toRadians(angle));
	double x =a*a+b*b-2*a*b*result;
	double ans = Math.sqrt(x);
	System.out.println(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