import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ

		Scanner sc = new Scanner(System.in);
		//入力表示

		double a = sc.nextInt();
		double b = sc.nextInt();
		double h = sc.nextInt();
		double m = sc.nextInt();

		double rad = Math.PI * 2 * (h / 12.0 + (m / 60.0) / 12.0 - m / 60.0);

		double rsq = Math.sqrt((a * a + b * b) - (2 * a *
				b) * Math.cos(rad));

		System.out.printf("%.20f", rsq);

	}
}
/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