
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 Hour = sc.nextInt();
    double Minute = sc.nextInt();

    double x1 = A * Math.cos(2 * Math.PI * (Hour + Minute / 60) / 12);
    double y1 = A * Math.sin(2 * Math.PI * (Hour + Minute / 60) / 12);
    double x2 = B * Math.cos(2 * Math.PI * Minute / 60);
    double y2 = B * Math.sin(2 * Math.PI * Minute / 60);
    
    System.out.println(Math.sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)));

  }
}
/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