#include <cassert>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <functional>
#include <iostream>
#include <limits>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

using Int = long long;

template <class T1, class T2> ostream &operator<<(ostream &os, const pair<T1, T2> &a) { return os << "(" << a.first << ", " << a.second << ")"; };
template <class T> ostream &operator<<(ostream &os, const vector<T> &as) { const int sz = as.size(); os << "["; for (int i = 0; i < sz; ++i) { if (i >= 256) { os << ", ..."; break; } if (i > 0) { os << ", "; } os << as[i]; } return os << "]"; }
template <class T> void pv(T a, T b) { for (T i = a; i != b; ++i) cerr << *i << " "; cerr << endl; }
template <class T> bool chmin(T &t, const T &f) { if (t > f) { t = f; return true; } return false; }
template <class T> bool chmax(T &t, const T &f) { if (t < f) { t = f; return true; } return false; }
#define COLOR(s) ("\x1b[" s "m")


constexpr int LIM = 1000;
int lpf[LIM];

constexpr int B = 10;
int ans[1 << B];

int main() {
  for (int p = 2; p < LIM; ++p) lpf[p] = p;
  for (int p = 2; p < LIM; ++p) if (lpf[p] == p) {
    for (int n = p; n < LIM; n += p) chmin(lpf[n], p);
  }
  
  memset(ans, ~0, sizeof(ans));
  int cnt = 0;
  for (int p = 2; p < LIM; ++p) if (lpf[p] == p) {
    int h = 0;
    for (int pp = p; pp; pp /= B) {
      h |= 1 << (pp % B);
    }
    h = ((1 << B) - 1) - h;
    if (!~ans[h]) {
      for (int g = h; ; --g &= h) {
        if (!~ans[g]) {
          ans[g] = p;
          ++cnt;
// cerr<<"cnt = "<<cnt<<", p = "<<p<<endl;
        }
        if (!g) break;
      }
    }
  }
// pv(ans,ans+(1<<B));
// for(int h=0;h<1<<B;++h)if(!~ans[h]){for(int x=0;x<B;++x)if(!(h>>x&1))cerr<<x;cerr<<endl;}
  
  int N;
  for (; ~scanf("%d", &N); ) {
    vector<int> D(N);
    for (int i = 0; i < N; ++i) {
      scanf("%d", &D[i]);
    }
    
    int h = 0;
    for (int i = 0; i < N; ++i) {
      h |= 1 << D[i];
    }
    printf("%d\n", ans[h]);
  }
  return 0;
}