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#include <bits/stdc++.h>
using namespace std;
typedef long long lld;
typedef double lf;
typedef long double llf;
typedef pair<int,int> pii;
typedef pair<lld,lld> pll;
#define For(i,s,a) for(int i = (int)s; i < (int)a; ++i)
#define rpt(s, it) for(auto it = s.begin(); it != s.end(); ++it)
#define brpt(s, it) for(auto it = s.rend(); it != s.rbegin(); --it)
#define sz size()
#define pb push_back
#define eb emplace_back
#define ff first
#define dd second
#define mp make_pair
#define all(x) (x).begin (x).end()
#define ZAPS {int t; scanf("%i", &t); while(t--) solve();}


template<typename Ta, typename Tb>
ostream & operator <<(ostream & os, pair<Ta, Tb> x){
	return os << x.ff << " " << x.dd;
}

const int N = 5e5 + 1;
const int inf = 0x3f3f3f3f;

lld power[N];
lld sum[N];
int dp[2][N];

const int H = 18e6;
const lld ran = (1ll << 50) - 1;

struct Tre{
	int nodes[H], left[H], right[H];
	int offset;
	int size;
	Tre(){
	}
	void clear(){
		memset(nodes, inf, sizeof(nodes));
		memset(left, 0, sizeof(left));
		memset(right, 0, sizeof(right));
		size = 1;
		offset = 0;
	}
	void push_all(){
		++nodes[1];
	}
	int get(lld a, lld b, int w = 1, lld L = -ran, lld R = ran){
		if(a <= L && R <= b){
			//cout<<offset<<" "<<nodes[w]<<"   "<<a<<" "<<b<<"   "<<L<<" "<<R<<endl;
			return offset + nodes[w];}
		if(L > b || R < a)
			return inf;
		lld mid = (L + R) >> 1ll;
		int wyn = inf;
		if(left[w])
			wyn = min(wyn, get(a, b, left[w], L, mid));
		if(right[w])
			wyn = min(wyn, get(a, b, right[w], mid + 1, R));
		return wyn;
	}
	void upd(lld pos, int score, int w = 1, lld L = -ran, lld R = ran){
		nodes[w] = min(nodes[w], score);
		if(L == R)
			return;
		lld mid = (L + R) >> 1ll;
		if(pos <= mid){
			if(!left[w])
				left[w] = ++size;
			upd(pos, score, left[w], L, mid);
		}
		else{
			if(!right[w])
				right[w] = ++size;
			upd(pos, score, right[w], mid + 1, R);
		}
	}
	void do_upd(lld pos, int score){
		++offset;
		score -= offset;
		this -> upd(pos, score);
	}
};

Tre tre;

lld pre(int a, int b){
	return sum[b] - (a ? sum[a - 1] : 0);
}

bool valid(int a, int b){
	return pre(a, b) >= 0;
}

void solve(int rot, int n){
	tre.clear();
	sum[0] = power[0];
	For(i, 1, n)
		sum[i] = sum[i - 1] + power[i];
	For(i, 0, n){
		dp[rot][i] = inf;
		if(valid(0, i)){
			//cout<<i<<" "<<rot<<" "<<sum[i]<<" "<<tre.get(-ran, sum[i])<<endl;
			dp[rot][i] = min(i, tre.get(-ran, sum[i]));
		}
		tre.do_upd(sum[i], dp[rot][i]);
		//cout<<rot<<" "<<i<<" "<<dp[rot][i]<<endl;
	//	cout<<dp[rot][i]<<" ";
	}
	//puts("");
}

int32_t main(void){
	int n;
	scanf("%d", &n);
	For(i, 0, n)
		scanf("%lld", &power[i]);
	solve(0, n);
	reverse(power, power + n);
	solve(1, n);
	reverse(dp[1], dp[1] + n);
	int wyn = inf;
	For(i, -1, n){
		wyn = min(wyn, (i > -1 ? dp[0][i] : 0) + (i + 1 < n ? dp[1][i + 1] : 0));
	}
	printf("%d\n", wyn == inf ? -1 : wyn);
}

/*
17
2 -5 0 2 0 0 0 4 0 0 -1 4 0 0 0 0 -3
*/