#include <iostream>
#include <vector>
#include <list>

using namespace std;

int main() {
	int n;
	cin >> n;
	vector<int> b(n);
	for (int i = 0; i < n; ++i) {
		cin >> b[i];
	}
	list<pair<int, int> > movables;
	for (int i = 0; i < n; ++i) {
		if (b[i] > 1) {
			movables.push_back(make_pair(i, b[i]));
		}
	}
	long long result = 0;
	for (int i = 0; i < n; ++i) {
		if (b[i] == 0) {
			list<pair<int, int> >::iterator it = movables.begin();
			result += abs(it->first - i);
			--it->second;
			if (it->second == 1) {
				movables.erase(it);
			}
		}
	}
	cout << result << endl;
	return 0;
}