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();
        sc.nextLine();

        double t = (double) H*5 + (double) M/12;
        double sa = Math.abs(t - M);

        if (sa > 30) {
            sa = 60 - sa;
        }

        sa *= 6.0;

        double ans = Math.pow(A, 2) + Math.pow(B, 2) - 2.0 * A * B * Math.cos(Math.toRadians(sa));

        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