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#include <bits/stdc++.h>
using namespace std;
#define REP(i,a,b) for (int i = (a); i <= (b); ++i)
#define REPD(i,a,b) for (int i = (a); i >= (b); --i)
#define FORI(i,n) REP(i,1,n)
#define FOR(i,n) REP(i,0,int(n)-1)
#define mp make_pair
#define pb push_back
#define pii pair<int,int>
#define vi vector<int>
#define ll long long
#define SZ(x) int((x).size())
#define DBG(v) cerr << #v << " = " << (v) << endl;
#define FOREACH(i,t) for (typeof(t.begin()) i=t.begin(); i!=t.end(); i++)
#define fi first
#define se second
typedef pair<ll,int> pli;

const int inf = 1000100;

int n;
int a[500500];

ll glob_x;
int glob_y;

set<pli> s;

void insert(int x, int y) {
	ll xr = -glob_x + x;
	int yr = y - glob_y;
	pli p(xr, -inf);
	auto it = s.lower_bound(p);
	while (it != s.begin()) {
		it--;
		if (it ->se >= yr) {
			auto it2=it;
			it++;
			s.erase(it2);
		} else {
			it++;
			break;
		}
	}
	p.se = yr;
	if (it == s.end()) {
		s.insert(p);
		return;
	}
	if (it -> fi == xr) {
		if (it -> se > yr) {
			s.erase(it);
			s.insert(p);
		}
		return;
	}
	if (it -> se > yr) {
		s.insert(p);
	}
}

void add(int p) {
	glob_x += p;
}

void incr() {
	glob_y++;
}

int get() {
	ll x0 = -glob_x;
	pli p(x0, -inf);
	auto it = s.lower_bound(p);
	if (it == s.end()) return inf;
	return it -> se + glob_y;
}

int main() {
	scanf("%d", &n);
	FORI(i,n) scanf("%d", &a[i]);
	insert(0,0);
	FORI(i,n) {
		int y = get();
		add(a[i]);
		incr();
		if (y<inf) {
			insert(a[i], y);
		}
		//for (auto it : s) { printf("(%lld, %d) ", it.fi+glob_x, it.se+glob_y); }
		//printf("\n");
	}
	int y = get();
	printf("%d\n", y==inf?-1:y);
	return 0;
}