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();
        sc.close();
        double l = m*6;
        double s = h*30+m*0.5;
        double cos;
        if (Math.abs(l-s) > 180) {
            cos = 360 - Math.abs(l-s);
        } else {
            cos = Math.abs(l-s);
        }
        double c2 = Math.pow(a, 2) + Math.pow(b, 2) - 2*a*b*Math.cos(Math.toRadians(cos));
        double c = Math.sqrt(c2);

        System.out.println(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