#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef pair<ll, ll> p_ll;

template<class T>
void debug(T itr1, T itr2) { auto now = itr1; while(now<itr2) { cout << *now << " "; now++; } cout << endl; }
#define repr(i,from,to) for (int i=(int)from; i<(int)to; i++)
#define all(vec) vec.begin(), vec.end()
#define rep(i,N) repr(i,0,N)
#define per(i,N) for (int i=(int)N-1; i>=0; i--)

const ll MOD = pow(10,9)+7;
const ll LLINF = pow(2,61)-1;
const int INF = pow(2,30)-1;

vector<ll> fac;
void c_fac(int x=pow(10,6)+10) { fac.resize(x,true); rep(i,x) fac[i] = i ? (fac[i-1]*i)%MOD : 1; }
ll inv(ll a, ll m=MOD) { ll b = m, x = 1, y = 0; while (b!=0) { int d = a/b; a -= b*d; swap(a,b); x -= y*d; swap(x,y); } return (x+m)%m; }
ll nck(ll n, ll k) { return fac[n]*inv(fac[k]*fac[n-k]%MOD)%MOD; }
ll gcd(ll a, ll b) { if (a<b) swap(a,b); return b==0 ? a : gcd(b, a%b); }
ll lcm(ll a, ll b) { return a/gcd(a,b)*b; }

// ----------------------------------------------------------------------
// ----------------------------------------------------------------------

vector<bool> isp;

void sieve(int x=pow(10,6)+10) {
  isp.resize(x,true); 
  isp[0] = false;
  isp[1] = false;
  for (int i=2; pow(i,2)<=x; i++) {
    if (isp[i]) for(int j=2; i*j<=x; j++) isp[i*j] = false;
  }
}

// ----------------------------------------------------------------------
// ----------------------------------------------------------------------

int main() {
  ll MNUM = 5*pow(10,6);
  sieve(MNUM+10);
  ll N; cin >> N;
  bool num[10] = {}; rep(i,N) { ll A; cin >> A; num[A] = true; }
  bool use[10] = {};

  bool ok = false;
  ll l = 1, result = -1, now;
  repr(i,1,MNUM+1) {
    if (isp[i]) {
      bool ok = true; 
      now = i; while (now) { ok &= num[now%10]; now /= 10; }
      if (ok) {
        now = i; while (now) { use[now%10] = true; now /= 10; }
      } 
      else {
        bool numok = true; rep(j,10) numok &= num[j]==use[j];
        if (numok) result = max(result, (i-1)-l);
        // cout << l << " ~ " << i << " "; debug(use,use+10);
        rep(j,10) use[j] = false;
        l = i+1;
      }
    }
  }
  bool numok = true; rep(j,10) numok &= num[j]==use[j];
  if (numok) result = max(result, MNUM-l);

  cout << result << endl;
  return 0;
}