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#include "bits/stdc++.h"
using namespace std;
template <class A, class B> ostream& operator<<(ostream &os, pair<A, B> p) {
  return os << '{' << p.first << ", " << p.second << '}';
}
template <class T> ostream& operator<<(ostream &os, vector<T> v) {
  os << '{';
  for (T i : v)
    os << i << ", ";
  return os << '}';
}
#ifdef DEBUG
#define D(x...) x
#else
#define D(x...)
#endif
#define LN(x) D(cerr << #x << ": " << x << ' ')
#define LOG(x) D(cerr << #x << ": " << x << '\n')
#define MES(x) D(cerr << x << ' ')
#define MESL(x) D(cerr << x << '\n')
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
#define EB emplace_back
#define PB pop_back
#define fi first
#define se second
#define FOR(i, a, b) for (int i = (a); i <= (b); ++i)
#define REP(i, n) FOR(i, 0, (n) - 1)

// Ignacy Boehlke

int main() {
    int n;
    scanf("%d", &n);

    int in, dis = 0, len = 0;
    ll sum = 0;
    set<pair<ll, int>> S;
    S.emplace(0, 0);
    auto it = S.begin();
    REP(i, n) {
        scanf("%d", &in);
        ++len;
        if (in == 0) continue;

        it = S.upper_bound({sum, INT_MAX});
        if (it != S.begin()) {
            --it;
            pair<ll, int> val = {sum, it->se + len};
            it = S.lower_bound({val.fi, INT_MAX});
            if (it == S.begin() || (--it)->se < val.se) {
                if (it->fi == val.fi) it = S.erase(it);
                else ++it;
                while (it != S.end() && it->se <= val.se) it = S.erase(it);
                S.emplace(val);
            }
        }

        sum += in;
        dis += len;
        len = 0;
        D(for (auto s : S) fprintf(stderr, "{%lld, %d}, ", s.fi, s.se); fprintf(stderr, "\n");)
    }

    it = S.upper_bound({sum, INT_MAX});
    if (it == S.begin()) puts("-1");
    else printf("%d\n", dis - (--it)->se);
}