import java.util.Scanner;

public class Main {

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		
		double a = sc.nextDouble();
		double b = sc.nextDouble();
		int h = sc.nextInt();
		int m = sc.nextInt();
		double num1 = 0.5*m + 30*h;
		double num2 = 6*m;
		double num3 = 0;
		
		if(num1 > num2) {
			num3 = num1 - num2;
		} else if (num2 > num1){
			num3 = num2 - num1;
		}
		
		if(num3 > 180) {
			num3 = 360- num3;
		}
		
		if(num1 == num2) {
			if(a > b) {
				System.out.println(a-b);
				return;
			} else if (b > a) {
				System.out.println(b-a);
				return;
			} else if (a == b) {
				System.out.println(0);
				return;
			}
		}
		
	

		double cos =  Math.cos(Math.toRadians(num3));
		double c = (a*a+b*b)-(2*a*b*cos);
		double ans = Math.sqrt(c);
		System.out.println(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