import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		try(Scanner scanner = new Scanner(System.in)) {
			int A = scanner.nextInt();
			int B = scanner.nextInt();
			int H = scanner.nextInt();
			int M = scanner.nextInt();

			double sita = ((double)H / 12 + (double)M / 12 / 60 - (double)M / 60) * 2 * Math.PI;
			sita = sita < 0 ? -(double)sita : sita;
			double answer = Math.sqrt((double)(Math.pow(A, 2) + Math.pow(B, 2) - (double)((double)(2 * A * B) * Math.cos(sita))));
			System.out.print(answer);
		}
	}
}
/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