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#include <bits/stdc++.h>
using namespace std;
#define PII pair<int, int>
#define VI vector<int>
#define VPII vector<PII>
#define LL long long
#define LD long double
#define f first
#define s second
#define MP make_pair
#define PB push_back
#define endl '\n'
#define ALL(c) (c).begin(), (c).end()
#define SIZ(c) (int)(c).size()
#define REP(i, n) for(int i = 0; i < (int)(n); ++i)
#define FOR(i, b, e) for(int i = (b); i <= (int)(e); ++i)
#define FORD(i, b, e) for(int i = (b); i >= (int)(e); --i)
#define ll LL
#define st f
#define nd s
#define pb PB
#define mp MP
#define eb emplace_back
#define siz(c) SIZ(c)
const int inf = 1e9+7;
const ll INF = 1e18L+7;

#define sim template<class n
sim, class s> ostream & operator << (ostream &p, pair<n, s> x)
{return p << "<" << x.f << ", " << x.s << ">";}
sim> auto operator << (ostream &p, n y) ->
typename enable_if<!is_same<n, string>::value, decltype(y.begin(), p)>::type 
{int o = 0; p << "{"; for(auto c: y) {if(o++) p << ", "; p << c;} return p << "}";}
void dor() {cerr << endl;}
sim, class...s> void dor(n p, s...y) {cerr << p << " "; dor(y...);}
sim, class s> void mini(n &p, s y) {if(p>y) p = y;}
sim, class s> void maxi(n &p, s y) {if(p<y) p = y;}
#ifdef DEB
#define debug(...) dor(__FUNCTION__, ":", __LINE__, ": ", __VA_ARGS__)
#else
#define debug(...)
#endif 

#define I(x) #x " =", (x), " "

#ifndef LOCAL
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace __gnu_pbds;

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

#else
#include</Users/dawid/algo/mac/ordered_set>
#endif

#define int ll
const int N = 1<<20;

int n;

int dp[N];
int a[N];
int sub[2*N];

void insert(int a, int v)
{
	a += N;

	while(a) 
	{
		maxi(sub[a], v);
		a /= 2;
	}
}

int query(int a, int b)
{
	a += N-1;
	b += N+1;

	int res = -inf;

	while(a<b-1)
	{
		if(a%2==0)
			maxi(res, sub[a+1]);

		if(b%2==1)
			maxi(res, sub[b-1]);

		a /= 2;
		b /= 2;
	}

	return res;
}

int32_t main()
{
	ios_base::sync_with_stdio(0);
	cin.tie(NULL);

	cin >> n;

	VI val;

	for(int i = 1; i <= n; ++i)
	{
		cin >> a[i];
		a[i] += a[i-1];
		val.pb(a[i]);
	}	

	sort(ALL(val));
	val.erase(unique(ALL(val)), val.end());

	for(int i = 0; i < 2*N; ++i)
		sub[i] = -inf;

	for(int i = 0; i <= n; ++i)
	{
		// debug(a[i]);
		a[i] = lower_bound(ALL(val), a[i]) - val.begin();
		
	}

	dp[0] = 0;

	insert(a[0], dp[0]);

	for(int i = 1; i <= n; ++i)
	{
		dp[i] = 1 + query(0, a[i]);
		insert(a[i], dp[i]);
	}

	if(dp[n] < 0)
		cout << -1 << endl;
	else 
		cout << n - dp[n] << endl;
}