import java.util.Scanner;
public class Main{
  public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int A = scan.nextInt();
    int B = scan.nextInt();
    int H = scan.nextInt();
    int M = scan.nextInt();
    double h = (H + (double)M/60)*30;
    double m = (double)M*6;
    double ans = Math.sqrt(A*A + B*B - 2*A*B*Math.cos(Math.toRadians(h-m)));
    System.out.println(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