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#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>

using namespace std;

int n;
long long s, a;

vector <long long> v;
vector <long long>::iterator it;

int main ()
{
	scanf("%d", &n);
	scanf("%lld", &s);
	v.push_back(0);
	for (int i = 1; i < n; ++i)
	{
		scanf("%lld", &a);
		if (s >= v.back()) v.push_back(s);
		else if (s >= 0)
		{
			it = upper_bound(v.begin(), v.end(), s);
			*it = s;
		}
		s += a;
	}
	if (s < 0)
	{
		printf("-1\n");
		return 0;
	}
	for (it = v.begin(); it != v.end(); ++it)
	{
		if (s >= *it) n--;
		else break;
	}
	printf("%d\n", n);
	return 0;
}