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();

		int pass_time = H*60 + M;
      	//1min =0.5°
		double digA = (0.5 * (double)pass_time) % 360;
      	//1min =6°
		double digB = (6 * pass_time) % 360;

		double C = Math.sqrt(A*A + B*B -2*A*B*Math.cos(Math.toRadians(Math.abs(digA-digB))));

		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