#include <bits/stdc++.h>
using namespace std;
int n, arr[2002], same, cnt, found, temp;
int gcd(int a, int b) {
  if (!b) return a;
  return gcd(b, a % b);
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cin >> n;
  for (int i = 0; i < n; ++i) cin >> arr[i];
  while (count(arr, arr + n, 1) != n) {
    same = 1;
    for (int i = 0; i < n - 1; ++i) {
      if (arr[i] != arr[i + 1]) same = 0;
      if (gcd(arr[i], arr[i + 1]) == 1 && arr[i] != arr[i + 1]) {
        ++cnt;
        found = 1;
        if (arr[i] != 1)
          arr[i] = 1;
        else
          arr[i + 1] = 1;
      }
    }
    if (same) return cout << -1, 0;
    if (!same && !found) {
      for (int i = 0; i < n - 1; ++i) {
        if (arr[i] != arr[i + 1]) {
          ++cnt;
          temp = gcd(arr[i], arr[i + 1]);
          if (i != n - 1 && gcd(temp, arr[i + 2]) == 1)
            arr[i + 1] = temp;
          else if (arr[i] > arr[i + 1] && arr[i] != temp)
            arr[i] = temp;
          else
            arr[i + 1] = temp;
        }
      }
    }
  }
  cout << cnt;
  return 0;
}
