public class Main {
	static double[][] m;
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		while (sc.hasNextInt()) {
			int num = sc.nextInt();
			
			m = new double[num + 1][num + 1];
			for (int i = 0; i < num + 1; i++)
				m[i] = new double[num + 1];

			int[] p = new int[num];
			for (int i = 0; i < num; i++)
				p[i] = sc.nextInt();
			System.out.println(ans(p));
		}
	}
	
	private static String ans(int[] p) {
		m[1][0] = (100 - p[0]) / 100.0;
		m[1][1] = p[0] / 100.0;
		
		for (int i = 2; i <= p.length; i++) {
			double fail = (100 - p[i - 1]) / 100.0;
			double suc = p[i - 1] / 100.0;
			m[i][0] = m[i - 1][0] * fail;
			for (int j = 1; j <= i; j++) {
				m[i][j] = m[i - 1][j] * fail + m[i - 1][j - 1] * suc;
			}
		}
		double res = 0;
		int suc = (int) Math.ceil(p.length * 0.6);
		for (int i = suc; i <= p.length; i++) res += m[p.length][i];
		
		DecimalFormat df = new DecimalFormat("0.00000");
		return df.format(res);
	}
}