#include <bits/stdc++.h>
using namespace std;

int main()
{
	int N;
	cin >> N;
	vector<int> A( N );
	for( int i = 0; i < N; i++ ) cin >> A[i];

	long long ans = 0;
	int cnt = 0;
	int f = 0;
	for( int i = 0; i < N - 1; i++ ) {
		if( f ) {
			if( f == 1 ) {
				if( A[i] == 0 ) {
					f = 0;
					cnt = 0;
				}
				else {
					f = 2;
					ans += cnt;
				}
			}
			else {
				if( A[i] ) {
					f = 0;
					cnt = 0;
					i--;
				}
				else {
					f = 1;
					ans += cnt;
					ans += 2;
					cnt++;
				}
			}
		}
		else {
			if( i + 1 < N - 1 && A[i] && A[i + 1] == 0 ) {
				cnt++;
				i++;
				f = 1;
				ans += cnt * 2;
			}
		}		
	}
	for( int i = 0; i < N - 1; i++ ) {
		if( (A[i] && A[i + 1]) || (A[i] && i + 1 == N - 1) ) ans++;
	}

	cout << ans << endl;
}