import java.util.*;
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();
    if(H>=12){H =H-12;}
    double K =Math.abs(H*30+M*0.5-M*6);
    double k =Math.cos(Math.toRadians(K));
    double T =A*A+B*B-2*A*B*k;
    double t =Math.sqrt(T);
    System.out.println(t);
  }
}
/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