import java.util.Scanner;

public class No1765 {

	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int N = Integer.valueOf(scan.nextLine());
		String[] S = scan.nextLine().split(" ");
		scan.close();
		int m0 = 0, m1 = 0;
		long cnt = 0;
		for (int i = 0; i < N-1; i++) {
			if (S[i].equals("1")) {
				cnt += 1 + m1;
				m0 = 1 + m1;
				m1 = 0;
			} else {
				cnt += m0;
				m1 = m0;
				m0 = 0;
			}
		}
		System.out.println(cnt);
	}
}