import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] a = new int[n];
		for (int i = 0; i < n; i++) {
			a[i] = sc.nextInt();
		}
		sc.close();

		if (n == 1) {
			System.out.println(0);
			return;
		}

		long[] num = new long[n + 1];
		num[1] = 1;
		num[2] = 2;
		for (int i = 3; i < num.length; i++) {
			num[i] = num[i - 2] + i;
		}

		long ans = 0;
		int cnt = 0;
		for (int i = 0; i < n - 1; i++) {
			if (cnt % 2 == 0) {
				if (a[i] == 1) {
					cnt++;
				} else {
					ans += num[cnt];
					cnt = 0;
				}
			} else {
				if (a[i] == 1) {
					ans += num[cnt];
					cnt = 1;
				} else {
					cnt++;
				}
			}
		}
		ans += num[cnt];
		System.out.println(ans);
	}
}