import java.util.Scanner;
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 ans;
        
        double sho = (H * 60 + M) * 360 / ( 12 * 60 );
        double lon = M * 360 / 60;
        double ang;
        
        ang = Math.abs(sho - lon);
        
        ans = Math.sqrt(A * A + B * B 
                - 2.0 * 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