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#include <bits/stdc++.h>
using namespace std;

void __print(int x) { cerr << x; }
void __print(int64_t x) { cerr << x; }
void __print(uint32_t x) { cerr << x; }
void __print(uint64_t x) { cerr << x; }
void __print(float x) { cerr << x; }
void __print(double x) { cerr << x; }
void __print(long double x) { cerr << x; }
void __print(char x) { cerr << '\'' << x << '\''; }
void __print(const char *x) { cerr << '\"' << x << '\"'; }
void __print(const string &x) { cerr << '\"' << x << '\"'; }
void __print(bool x) { cerr << (x ? "true" : "false"); }

template<typename T, typename V>
void __print(const pair<T, V> &x) { cerr << '('; __print(x.first); cerr << ", "; __print(x.second); cerr << ')'; }
template<typename T>
void __print(const T &x) { int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? ", " : ""), __print(i); cerr << "}"; }
void _print() { cerr << "]\n"; }
template <typename T, typename... V>
void _print(T t, V... v) { __print(t); if (sizeof...(v)) cerr << ", "; _print(v...); }

#define debug(x...) cerr << " > [" << #x << "] = ["; _print(x)

vector<int64_t> a, pref, dp;
int n;
const int64_t oo = 1e9;
map<int64_t, int> sc;

inline int64_t sum(int l, int r) { return pref[r + 1] - pref[l]; }

const int TREE_SIZE = (1 << 19);

int64_t tree[2 * TREE_SIZE + 1];

int64_t min(int node, int left, int right, int l, int r) {
    if(left > r or right < l) {
        return oo;
    }
    if(left >= l and right <= r) {
        return tree[node];
    }
    int mid = (left + right) / 2;
    return min(min(2 * node, left, mid, l, r), min(2 * node + 1, mid + 1, right, l, r));
}

void change(int node, int64_t val) {
    node += TREE_SIZE;
    while(node) {
        tree[node] = min(tree[node], val);
        node >>= 1;
    }
}

void init() {
    int timer = 0;
    for(auto &p : sc) {
        p.second = timer++;
    }
    for(int i = 0; i < 2 * TREE_SIZE; i++) {
        tree[i] = oo;
    }
}

int main() {
    ios_base::sync_with_stdio(false); cin.tie(nullptr);

    cin >> n;
    a.resize(n);
    pref.resize(n + 1);
    dp.resize(n);
    sc[0];
    for(int i = 0; i < n; i++) {
        cin >> a[i];
        pref[i + 1] = pref[i] + a[i];
        sc[pref[i + 1]];
    }
    init();
    if(a[0] < 0) dp[0] = oo;
    else dp[0] = 0;
    change(sc[pref[1]], dp[0] - 1);
    for(int i = 1; i < n; i++) {
        if(sum(0, i) < 0) dp[i] = oo;
        else dp[i] = 0;
        dp[i] = min(dp[i], min(1, 0, TREE_SIZE - 1, 0, sc[pref[i + 1]]));
        change(sc[pref[i + 1]], dp[i] - 1);
    };
    dp[n - 1] += n - 1;
    if(dp[n - 1] > n) dp[n - 1] = -1;
    cout << dp[n - 1];

    return 0;
}