import java.util.Scanner;
public class Main {

	public static void main(String[] args) {

		Scanner scan = new Scanner(System.in);

		int a = scan.nextInt();
		int b = scan.nextInt();
		int hour = scan.nextInt();
		int minute = scan.nextInt();

		double rad = Math.PI*2*((double)hour/12.0 + ((double)minute/60.0)/12.0 - (double)minute/60.0);
		double len = (double)(b*b + a*a) - (double)(2*b*a)*Math.cos(rad);

		System.out.printf("%.20f",Math.sqrt(len));
		scan.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