import java.util.*;
public class Main{
	public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int a = Integer.parseInt(sc.next());
        int b = Integer.parseInt(sc.next());
        double h = Double.parseDouble(sc.next());
        double m = Double.parseDouble(sc.next());
        double res = Math.sqrt(
                Math.pow(a, 2) + Math.pow(b, 2) - 2 * a * b * Math.cos(Math.abs((h + m / 60) / 12 - m / 60) * 2 * Math.PI));
        System.out.println(res);  
    }
}
/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