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 HR = 30 * H + M * 0.5;
        double MR = 360 / 60 * M;

        double r = Math.abs(HR - MR);
        double cos = Math.cos(Math.toRadians(r));
        double result = Math.pow(A, 2) + Math.pow(B, 2) - 2 * A * B * cos;
        result = Math.sqrt(result);
       
       
        System.out.println(result);
    }
}
/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