import java.util.Scanner;

public class Main {
	static Scanner scan = new Scanner(System.in);
	
	public static void main(String[] args) {
		final int n = scan.nextInt();
		final int[] arr = new int[n];
		long ans = 0;
		for(int i=0; i<n; i++) {
			arr[i] = scan.nextInt();
		}
		for(int i=0; i<n; i++) {
		    ans += move(arr, n-1, i);   
		}
		System.out.println(ans);
	}
	static long move(int[] arr, int n , int i) {
		int j = i;
		while(true) {
			if(j >= n) { j = n; break; }
			if(arr[j] == 0) break;
			if(arr[j+1] == 1) { j++; break; }
			j+=2;
		}
		return j-i;
	}
}