#include <bits/stdc++.h>
using namespace std;
const int mx = 1e6 + 10;
int n, m;
int a[mx], b[mx];
long long pre[mx], cnt[mx];
vector<int> pri;
vector<long long> g;
bool vis[mx];
void init() {
  for (int i = 2; i < mx; i++) {
    if (!vis[i]) pri.push_back(i);
    for (int j : pri) {
      if (j * i >= mx) break;
      vis[j * i] = 1;
      if (i % j == 0) break;
    }
  }
}
long long get_ans(long long val) {
  long long sum = 0;
  for (int i = 1; i <= n; i++) {
    b[i] = a[i] % val;
    sum += b[i];
    pre[i] = pre[i - 1] + 1ll * b[i] * i;
    cnt[i] = cnt[i - 1] + b[i];
  }
  long long siz = sum / val;
  long long ans = 0, pv = 0, ret = 0;
  int pp = 1;
  for (int i = 1; i <= siz; i++, ret += val) {
    int midk = lower_bound(cnt + pp, cnt + 1 + n, ret + (val + 1) / 2) - cnt;
    int k = lower_bound(cnt + midk, cnt + n + 1, ret + val) - cnt;
    long long mv = max(0ll, cnt[k] - (ret + val));
    long long lv = pre[midk] - pv;
    ans += midk * (cnt[midk] - ret) - lv;
    long long rv = pre[k] - mv * k - pre[midk];
    ans += rv - midk * (cnt[k] - cnt[midk] - mv);
    pv = pre[k] - mv * k, pp = k;
  }
  return ans;
}
int main() {
  scanf("%d", &n);
  init();
  long long sum = 0;
  for (int i = 1; i <= n; i++) {
    scanf("%d", a + i);
    sum += a[i];
  }
  long long tmp = sum, ans = 2e18;
  for (int i : pri) {
    if (tmp % i == 0) g.push_back(i);
    while (tmp % i == 0) tmp /= i;
  }
  if (tmp != 1) g.push_back(tmp);
  for (long long i : g) {
    ans = min(ans, get_ans(i));
  }
  printf("%lld\n", ans == 2e18 ? -1 : ans);
  return 0;
}
