 import java.util.Scanner;

public class Main {
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int A=sc.nextInt();
    int B=sc.nextInt();
    int H=sc.nextInt();
    int M=sc.nextInt();
    double x=M*6;
    double y=H*30+M*0.5;
    double t=Math.abs(x-y);
    double rad=t*3.141592653589/180;
    double cos=Math.cos(rad);
    double X=Math.sqrt((A*A)+(B*B)-(2*A*B*cos));
    System.out.println(X);
  }
}  
/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