#include <bits/stdc++.h>
using namespace std;
const int _ = 1e2;
const int maxn = 3e5 + _;
const int mod = 998244853;
inline int ad(int x, int y) { return x >= mod - y ? x - mod + y : x + y; }
inline int re(int x, int y) { return x < y ? x - y + mod : x - y; }
inline int mu(int x, int y) { return (long long)x * y % mod; }
inline int qp(int x, long long y) {
  int r = 1;
  while (y) {
    if (y & 1) r = mu(r, x);
    x = mu(x, x);
    y >>= 1;
  }
  return r;
}
inline int iv(int x) { return qp(x, mod - 2); }
inline int dv(int x, int y) { return mu(x, qp(y, mod - 2)); }
inline int gcd(int x, int y) { return x ? gcd(y % x, x) : y; }
int fac[maxn], fac_inv[maxn];
int C(int n, int m) {
  if (n < m) return 0;
  return mu(fac[n], mu(fac_inv[m], fac_inv[n - m]));
}
void yu() {
  fac[0] = 1;
  for (int i = 1; i < maxn; i++) fac[i] = mu(fac[i - 1], i);
  fac_inv[maxn - 1] = iv(fac[maxn - 1]);
  for (int i = maxn - 2; i >= 0; i--) fac_inv[i] = mu(fac_inv[i + 1], i + 1);
}
int f[10][maxn], num[maxn];
int main() {
  yu();
  int n, x, m = 0;
  scanf("%d", &n);
  for (int i = 1; i <= n; i++) {
    scanf("%d", &x);
    m = max(m, x);
    for (int j = 1; j * j <= x; j++)
      if (x % j == 0) {
        num[j]++;
        if (j * j != x) num[x / j]++;
      }
  }
  int ans = -1;
  for (int i = 1; i <= 7; i++) {
    for (int j = m; j >= 1; j--) {
      f[i][j] = C(num[j], i);
      for (int k = j + j; k <= m; k += j) f[i][j] = re(f[i][j], f[i][k]);
    }
    if (f[i][1]) {
      ans = i;
      break;
    }
  }
  printf("%d\n", ans);
  return 0;
}
