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#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp> // Common file
#include <ext/pb_ds/tree_policy.hpp> // Including tree_order_statistics_node_update

using namespace std;
using namespace __gnu_pbds;

typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update>
ordered_set;	

struct splitmix64_hash {
	static uint64_t splitmix64(uint64_t x) {
		// http://xorshift.di.unimi.it/splitmix64.c
		x += 0x9e3779b97f4a7c15;
		x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
		x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
		return x ^ (x >> 31);
	}
 
	size_t operator()(uint64_t x) const {
		static const uint64_t FIXED_RANDOM = std::chrono::steady_clock::now().time_since_epoch().count();
		return splitmix64(x + FIXED_RANDOM);
	}
};
 
template <typename K, typename V, typename Hash = splitmix64_hash>
using hash_map = __gnu_pbds::gp_hash_table<K, V, Hash>;
 
template <typename K, typename Hash = splitmix64_hash>
using hash_set = hash_map<K, __gnu_pbds::null_type, Hash>;

#define FOR(i,a,b) for(int i = (a); i <= (b); ++i)
#define FORD(i,a,b) for(int i = (a); i >= (b); --i)
#define RI(i,n) FOR(i,1,(n))
#define REP(i,n) FOR(i,0,(n)-1)
#define mini(a,b) a=min(a,b)
#define maxi(a,b) a=max(a,b)
#define pb push_back
#define st first
#define nd second
#define sz(w) (int) w.size()
typedef vector<int> vi;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<pii, int> para;
const ll inf = 1e18 + 7;
const ll maxN = 1e6 + 5;
const ll MOD = 1e9 + 7;

int n, a[maxN];
ll prefSum[maxN];
map<ll, int> mp;

template<typename T>
struct SegmentTree {
	
	SegmentTree(int _n) : n(_n) { 
		t.resize(n * 4); 
		fill(t.begin(), t.end(), MOD);
	}
	
	int n;
	vector<T> t;
	
	T query(int l, int r) {
		assert(l >= 1 && r <= n && l <= r);
		return _query(1, 1, n, l, r);
	}
	
	T _query(int v, int tl, int tr, int l, int r) {
	    if (l > r) 
	        return MOD;
	    if (l == tl && r == tr) {
	        return t[v];
	    }
	    int tm = (tl + tr) / 2;
	    return min(_query(v*2, tl, tm, l, min(r, tm))
	              ,_query(v*2+1, tm+1, tr, max(l, tm+1), r));
	}
	
	void update(int pos, T new_val) {
		assert(pos >= 1 && pos <= n);
		_update(1, 1, n, pos, new_val);
	}
	
	void _update(int v, int tl, int tr, int pos, T new_val) {
	    if (tl == tr) {
	        t[v] = min(new_val, t[v]);
	    } else {
	        int tm = (tl + tr) / 2;
	        if (pos <= tm)
	            _update(v*2, tl, tm, pos, new_val);
	        else
	            _update(v*2+1, tm+1, tr, pos, new_val);
	        t[v] = min(t[v*2], t[v*2+1]);
	    }
	}
};

// sprawdz MODULO!
int main() {
    mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
	ios_base::sync_with_stdio(0);
	cin.tie(0); cout.tie(0);
	cin >> n;
	vector<ll> vec;
	RI(i, n) {
		cin >> a[i];
		prefSum[i] = prefSum[i - 1] + a[i];	
		vec.pb(prefSum[i]);
	}
	vec.pb(0);
	sort(vec.begin(), vec.end());
	int cnt = 1;
	REP(i, n + 1) {
		if (!mp.count(vec[i]))
			mp[vec[i]] = cnt++;
	}
	SegmentTree<int> st(cnt);
	st.update(mp[0], -1);
	int ans = 0;
	RI(i, n) {
		int x = mp[prefSum[i]];
		int val = st.query(1, x) - 1;
		st.update(x, val);
		if (i == n) ans = val;
	}
	if (ans >= n) cout << -1 << "\n";
	else cout << ans + n + 1;
	return 0;
}