import java.util.*;
 
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 t1 = (h + m / 60.0) / 12.0;
		double t2 = m / 60.0;
		// System.out.println(t1);
		// System.out.println(t2);
		double r = Math.toRadians(Math.abs(t2 - t1) * 360.0);
		// System.out.println(r);
		double ans = a * a + b * b - 2 * a * b * Math.cos(r);
		System.out.println(Math.sqrt(ans));
	}
}
 
 
 
 
 
 
 
 
 
 

/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