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#include "bits/stdc++.h"
using namespace std;
using LL = long long;
#define FOR(i, l, r) for(int i = (l); i <= (r); ++i)
#define REP(i, n) FOR(i, 0, (n) - 1)
template<class T> int size(T &&x) {
	return int(x.size());
}
template<class A, class B> ostream& operator<<(ostream &out, const pair<A, B> &p) {
	return out << '(' << p.first << ", " << p.second << ')';
}
template<class T> auto operator<<(ostream &out, T &&x) -> decltype(x.begin(), out) {
	out << '{';
	for(auto it = x.begin(); it != x.end(); ++it)
		out << *it << (it == prev(x.end()) ? "" : ", ");
	return out << '}';
}
void dump() {}
template<class T, class... Args> void dump(T &&x, Args... args) {
	cerr << x << ";  ";
	dump(args...);
}
#ifdef DEBUG
  struct Nl{~Nl(){cerr << '\n';}};
# define debug(x...) cerr << (strcmp(#x, "") ? #x ":  " : ""), dump(x), Nl(), cerr << ""
#else
# define debug(...) 0 && cerr
#endif
mt19937_64 rng(0);
int rd(int l, int r) {
	return uniform_int_distribution<int>(l, r)(rng);
}
// end of templates

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(nullptr);
	
	int n; cin >> n;
	vector<int> vec(n), pref, cost;
	REP(i, n) cin >> vec[i];
	int cnt = 0;
	for(int x: vec) {
		if(x != 0) {
			if(cnt) cost.emplace_back(cnt);
			pref.emplace_back(x);
			cnt = 1;
		} else cnt++;
	}
	int m = size(pref);
	debug(pref, cost);

	//FOR(i, 1, m-1) pref[i] += pref[i-1];
	debug(pref);

	int ans = -1;
	REP(msk, (1 << (m-1))) {
		int temp = 0, sum = pref[0];
		REP(i, m-1) {
			if((msk >> i) & 1) {
				if(sum < 0) {
					temp = -1;
					break;
				} else {
					sum = pref[i+1];
					temp += cost[i];
				}
			} else
				sum += pref[i+1];
		}
		if(sum < 0) temp = -1;

		ans = max(ans, temp);
	}
	cout << (ans == -1 ? ans : n-1-ans) << '\n';
}