import java.util.*;
public class Main{
    public static void main(String[] args){
        Scanner input=new Scanner(System.in);
        int A=input.nextInt();
        int B=input.nextInt();
        int H=input.nextInt();
        int M=input.nextInt();
        double angle=Math.abs(5.5*M-H*30)%360;
        double c=Math.sqrt(A*A+B*B-2*A*B*Math.cos(Math.PI*angle/180));
      System.out.print(c);
    }   
}
/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