import java.util.Arrays;
import java.util.Scanner;

public class NickyEnMark {
	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		int n = scanner.nextInt();
		int m = scanner.nextInt();
		int k = scanner.nextInt();
		int[] s = new int[n];
		double ss = 0;
		for (int i = 0; i < n; i++) {
			s[i] = scanner.nextInt();
			ss += s[i];
		}

		Arrays.sort(s);

		if (m + k >= n) {
			System.out.println(100);
		} else {
			double sss = 0;
			for (int i = 0; i < m + k; i++) {
				sss += s[n - i - 1];
			}

			System.out.println(sss / ss * 100);
		}
	}
}