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#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

#define rep(i,poczatek,koniec)  for(__typeof(koniec) i = poczatek; i<=koniec; ++i)
#define repr(i,poczatek,koniec) for(__typeof(koniec) i = poczatek; i>=koniec; --i)
#define pb push_back
#define pob pop_back
#define eb emplace_back
#define pf push_front
#define pof pop_front
#define st first
#define nd second
#define bend(X) X.begin(),X.end()
#define sz(X) (int(X.size()))
#define graph vector<node>
#define print cout<<
#ifdef LOCAL
#define nl endl
#define dbg(x) cout << #x << " = " << x << ' ';
#define say(x) cout << x
#else
#define nl '\n'
#define dbg(x)
#define say(x)
#endif

using namespace std;
using namespace __gnu_pbds;

using ll 	= long long;
using ull 	= unsigned long long;
using ld 	= long double;
using pii 	= pair<int,int>;
using pll 	= pair<ll,ll>;
using pli	= pair<ll,int>;
using vb 	= vector<bool>;
using vc 	= vector<char>;
using vi 	= vector<int>;
using vl 	= vector<ll>;
using vpi 	= vector<pii>;
using vpl	= vector<pll>;
using vvi	= vector<vi>;
using vvl 	= vector<vl>;
using vvb	= vector<vb>;

template <typename T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag,tree_order_statistics_node_update>;

template<typename T1, typename T2> istream& operator>>(istream& is, pair<T1,T2>& x){
	is >> x.st >> x.nd;
	return is;
}
template<typename T1, typename T2> ostream& operator<<(ostream& os, pair<T1,T2>& x){
	os << '(' << x.st << ',' << x.nd << ')';
	return os;
}
template<typename T> istream& operator>>(istream& is, vector<T>& x){
	for(T& i : x)is >> i;
	return is;
}
template<typename T> ostream& operator<<(ostream& os, vector<T> x){
	for(T& i : x)os << i << ' ';
	return os;
}
template<typename T1, typename T2> pair<T1,T2> operator+(const pair<T1,T2>& A, const pair<T1,T2>& B){
	return {A.st + B.st, A.nd + B.nd}; 
}
template<typename T1, typename T2> pair<T1,T2> operator-(const pair<T1,T2>& A, const pair<T1,T2>& B){
	return {A.st - B.st, A.nd - B.nd}; 
}
template<typename T1, typename T2> pair<T1,T2> operator-(const pair<T1,T2>& A){
	return {-A.st, -A.nd};
}
template<typename T1, typename T2> void mine(T1& A, const T2& B){if(B < A) A = B;}
template<typename T1, typename T2> void maxe(T1& A, const T2& B){if(B > A) A = B;}

const int INF 	= (int)2e9;
const ll INFll 	= (ll)9e18;
const int MOD 	= (int)1e9+7;

void fastDataTransfer(){
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
}

#define val first
#define lazy second

const int war19 = 1<<19;
const int war20 = 1<<20;
int MAXI  = 1e6;

int n, m, a, b, c, d, q, k;
vi V,dp;
vpi T;
vl pref;
map<ll,int>M;
int POT=1;

void propagade(int v){
	if(v > POT || T[v].lazy == 0)
		return;
	for(int i : {v*2, v*2+1}){
		T[i].lazy += T[v].lazy;
		T[i].val += T[v].lazy;
	}
	T[v].lazy=0;
}

void update(int v){
	if(v>POT)
		return;
	for(int i : {v*2, v*2+1})
		mine(T[v].val, T[i].val);
}

int MINI,L,R;

void wartosc(int v, int l, int r){
	if(l>=L && r<=R){
		mine(MINI, T[v].val);
		return;
	}
	if(l>R || r < L)
		return;
	propagade(v);
	wartosc(v*2, l, (l+r)/2);
	wartosc(v*2+1, (l+r)/2 + 1, r);
}

void ustaw(int v, int l, int r){
	if(l>=L && r<=R){
		mine(T[v].val, MINI);
		return;
	}
	if(l>R || r<L)
		return;
	propagade(v);
	ustaw(v*2, l, (l+r)/2);
	ustaw(v*2+1, (l+r)/2 + 1, r);
	update(v);
}

void read(){
	cin>>n;
	V.resize(n);
	pref.resize(n+1);
	dp.resize(n+1);
	cin>>V;
	rep(i,1,n){
		pref[i]=pref[i-1]+V[i-1];
		M[pref[i]];
	}
	M[0];
	for(auto& i : M)
		i.nd = a++;
	while(POT<=M.size()){
		POT*=2;
	}
	T.resize(POT*2 + 5);
	for(auto& i : T){
		i.val = MAXI;
		i.lazy = 0;
	}
}

void wypiszDrzewo(){
	int i = 1;
	while(i<=POT){
		rep(j,i,i+i-1)
			print T[j] << ' ';
		print nl;
		i*=2;
	}
	print nl;
}

void solve(){
	if(pref.back() < 0){
		print -1 << nl;
		exit(0);
	}
	MINI = 0;
	L = R = M[0];
	ustaw(1,0,POT-1);
	rep(i,1,n){
		L = 0;
		R = M[pref[i]];
		MINI = MAXI;
		wartosc(1,0,POT-1);
		dp[i] = MINI;
		if(pref[i]-pref[i-1] >= 0)
			mine(dp[i], dp[i-1]);
		L = R;
		MINI = dp[i];
		T[1].lazy++;
		ustaw(1,0,POT-1);
	}
	print dp.back() << nl;
}

int main(){
	fastDataTransfer();
	int testCases = 1;
//	cin >> testCases;
	rep(testNumber, 1, testCases){
		read();
		solve();
	}
}