import java.util.*;
public class Main {
	public static void main(String[] args){
		Scanner sc=new Scanner(System.in);
		
		double a=sc.nextInt();
		double b=sc.nextInt();
		double h=sc.nextInt();
		double m=sc.nextInt();
		
		double t=h*60+m;
		
		
		//double hx = Math.sin(Math.toRadians(t*0.5))*3;
		//double hy = Math.cos(Math.toRadians(t*0.5))*3;
		double hx = Math.cos(Math.toRadians(t*0.5-90))*a;
		double hy = Math.sin(Math.toRadians(t*0.5-90))*a;
		//System.out.println(hx);
		//System.out.println(hy);
		
		//double mx = Math.sin(Math.toRadians(t/6))*4;
		//double my = Math.cos(Math.toRadians(t/6))*4;
		double mx = Math.cos(Math.toRadians(t*6-90))*b;
		double my = Math.sin(Math.toRadians(t*6-90))*b;
		//System.out.println(mx);
		//System.out.println(my);
		
		double d = Math.sqrt((hy-my)*(hy-my)+(hx-mx)*(hx-mx));
		System.out.println(d);
		
	}

}

/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