import java.util.Scanner;

public class Main {
	public static void main(String[] args){
		Scanner in = new Scanner(System.in);
		int a = in.nextInt();
		int b = in.nextInt();
		int h = in.nextInt();
		int m = in.nextInt();
		double h_ang = (h*30) + (m*0.5);
		double m_ang = m*6;
		double tmp = 0;
		if(h>m){
			tmp = h_ang - m_ang;
		}else{
			tmp = m_ang - h_ang;
		}
		if(tmp>180){
			tmp-=360;
		}
		double cos = Math.cos(Math.toRadians(tmp));
		double result = (a*a) + (b*b) - (2*a*b*cos);
		System.out.println(Math.sqrt(result));
	}
}

/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