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();
        double hAngle = 30 * H;
        double mAngle = 6 * M;

        hAngle += 30 * (mAngle / 360);
        
        double angle = Math.abs(hAngle - mAngle);
        double rad = Math.toRadians(angle);
        double cos = Math.cos(rad);
        double x = Math.pow(A,2) + Math.pow(B,2) - 2*A*B *cos;

        System.out.println(Math.sqrt(x));
    }
}
/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