import java.util.Scanner;

public class Main{
    public static void main(String[] args){
        final Scanner sc=new Scanner(System.in);

        final double A = Integer.parseInt(sc.next());
        final double B = Integer.parseInt(sc.next());
        final double H = Integer.parseInt(sc.next());
        final double M = Integer.parseInt(sc.next());

        double parseH = H * 30d + (30d * (M / 60d));
        double parseM = M * 6d;

        double ang = Math.abs(parseH - parseM);
        double ans = Math.sqrt(Math.pow(A, 2) + Math.pow(B, 2) -2d * A * B * Math.cos(Math.toRadians(ang)));
        System.out.print(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