import java.util.Scanner;
import java.util.Arrays;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
import java.util.HashSet;

class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    Double A=sc.nextDouble();
    Double B=sc.nextDouble();
    Double H=sc.nextDouble();
    Double M=sc.nextDouble();
    Double kakudo=Math.abs(H*30+30*(M/60)-M*6);
    if(kakudo>360-kakudo){
      kakudo=360-kakudo;
    }


    System.out.println(Math.sqrt(Math.pow(A,2)+Math.pow(B,2)-2*A*B*Math.cos(Math.toRadians(kakudo))));

  }
}

/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