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 mm = h + (m / 60.0) ;
        double cc = Math.cos((5 * mm - m) * Math.PI / 30.0);
        double z = Math.sqrt(a * a * 1.0 + b * b - 2.0 * a * b * cc);
        System.out.println(z);
        sc.close();
    }
}
/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