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