#include <bits/stdc++.h>
using namespace std;
template <typename T>
inline void read(T &x) {
  char c;
  bool nega = 0;
  while ((!isdigit(c = getchar())) && (c != '-'))
    ;
  if (c == '-') {
    nega = 1;
    c = getchar();
  }
  x = c - 48;
  while (isdigit(c = getchar())) x = x * 10 + c - 48;
  if (nega) x = -x;
}
template <typename T>
inline void writep(T x) {
  if (x > 9) writep(x / 10);
  putchar(x % 10 + 48);
}
template <typename T>
inline void write(T x) {
  if (x < 0) {
    putchar('-');
    x = -x;
  }
  writep(x);
  putchar(' ');
}
template <typename T>
inline void writeln(T x) {
  write(x);
  putchar('\n');
}
template <typename R, typename D>
inline void Min(R &a, D b) {
  if (a > b) a = b;
}
template <typename D, typename R>
inline void Max(D &a, R b) {
  if (a < b) a = b;
}
const int N = 100005;
int n;
vector<int> ans;
unordered_set<int> se, se2;
int main() {
  ios_base::sync_with_stdio(NULL);
  cin.tie(NULL);
  cout.tie(NULL);
  cin >> n;
  ans.push_back(0);
  for (int i = 1; i <= n; ++i) {
    int x;
    cin >> x;
    if (x < 0) {
      if (!se.count(-x)) return !(cout << -1);
      se.erase(-x);
    } else {
      if (se2.count(x)) return !(cout << -1);
      se2.insert(x);
      se.insert(x);
    }
    if (se.empty()) {
      ans.push_back(i);
      se2.clear();
    }
  }
  if (se.size()) return !(cout << -1);
  cout << ans.size() - 1 << '\n';
  for (int i = 1; i < ans.size(); ++i) cout << ans[i] - ans[i - 1] << ' ';
  return 0;
}
