import java.util.*;
import java.io.*;

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();

		//ここから角度を求める計算
		double minAngle = (double)M * 6;
		double onlyHour = (double)H * 30;
		double hourAngle = onlyHour + (double)M * 0.5;
		double angle = Math.abs(minAngle - hourAngle);
		if(angle > 180)
		angle = 360 - angle;

		//ここから長さを求める計算
		double ans = Math.sqrt(A * A + B * B - 2 * A * B * Math.cos(Math.toRadians(angle)));
		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