#include <iostream>
#include <vector>
using namespace std;
int main(void) {
	int n;
	cin >> n;
	vector<int> b(n);
	for (int i = 0; i < n; ++i) cin >> b[i];
	int ans = 0;
	for (int i = 0; i < n; ++i) {
		if (b[i] == 0) {
			for (int j = 0; j < i; ++j) {
				if (b[j] > 1) {
					--b[j], ++b[i];
					ans += i - j;
					break;
				}
			}
			if (b[i] == 0) {
				for (int j = i + 1; j < n; ++j) {
					if (b[j] > 0) {
						--b[j], ++b[i];
						ans += j - i;
						break;
					}
				}
			}
		}
	}
	cout << ans << endl;
	return 0;
}