#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("unroll-loops")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("O0")
#pragma GCC optimize("O1")
long long pw(int a, int b) {
  long long ret = 1;
  long long mul = a;
  while (b > 0) {
    if (b & 1) ret *= mul;
    mul *= mul;
    b /= 2;
  }
  return ret;
}
long long to_int(string s) {
  long long ret = 0;
  for (int(i) = (0); (i) < (s.size()); (i)++) {
    ret += pw(10, s.size() - i - 1) * (long long)(s[i] - '0');
  }
  return ret;
}
const int MAXN = 3e5 + 35;
int n, a[MAXN], dp[MAXN], cnt[MAXN], lp[MAXN];
vector<int> pr;
int main() {
  for (int(i) = (0); (i) < (MAXN); (i)++) dp[i] = MAXN;
  for (int(i) = (2); (i) < (MAXN); (i)++) {
    if (lp[i] == 0) {
      lp[i] = i;
      pr.push_back(i);
    }
    for (int j = 0; j < pr.size() and pr[j] <= lp[i] and i * pr[j] < MAXN; j++)
      lp[i * pr[j]] = lp[i];
  }
  cin >> n;
  for (int(i) = (0); (i) < (n); (i)++) cin >> a[i], cnt[a[i]]++;
  for (int(i) = (1); (i) < (MAXN); (i)++) {
    for (int j = 2 * i; j < MAXN; j += i) cnt[i] += cnt[j];
  }
  dp[1] = 0;
  for (int(i) = (2); (i) < (MAXN); (i)++) {
    int p = i;
    vector<int> pf;
    while (p > 1) {
      int tmp = lp[p];
      pf.push_back(tmp);
      while (p % tmp == 0) p /= tmp;
    }
    int c = 0;
    for (int(mask) = (1); (mask) < ((1 << pf.size())); (mask)++) {
      int tmp = 1;
      for (int(j) = (0); (j) < (pf.size()); (j)++) {
        if (mask & (1 << j)) tmp *= pf[j];
      }
      if (__builtin_popcount(mask) % 2 == 0)
        c -= cnt[tmp];
      else
        c += cnt[tmp];
    }
    if (c < n) {
      dp[i] = 1;
    }
  }
  for (int(i) = (2); (i) < (MAXN); (i)++) {
    for (int j = 2 * i; j < MAXN; j += i) {
      if (dp[j / i] == 1) dp[j] = min(dp[j], dp[i] + 1);
    }
  }
  int ans = MAXN;
  for (int(i) = (0); (i) < (n); (i)++) ans = min(ans, dp[a[i]] + 1);
  if (ans == MAXN)
    cout << -1 << "\n";
  else
    cout << ans << "\n";
}
