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 h = 30 * (H + M/60.0);
        double m = M * 6.0;
        double k = Math.abs(m - h);
        double cos = Math.cos(Math.toRadians(k));
        double a = A*A + B*B - (2*A*B*cos);
        System.out.println(Math.sqrt(a));
    }

}
/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