import java.util.Scanner;
class Main{
    static Scanner sc=new Scanner(System.in);
    public static void main(String[] args){
        int A = sc.nextInt();
        int B = sc.nextInt();
        double H = 5*sc.nextDouble();
        double M = sc.nextDouble();
        H = H+M/12;
      	double RAD =Math.toRadians((M-H)*6);
        double COS = Math.cos(RAD);
        double ans = (A*A)+(B*B)-(2*A*B*COS);
        ans = Math.sqrt(ans);
      	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