#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef ll li;
typedef pair<ll,ll> PI;
#define rep(i,n) for(int i=0;i<(int)(n);++i)
#define REP(i, n) rep (i, n)
#define F first
#define S second
#define mp(a,b) make_pair(a,b)
#define pb(a) push_back(a)
#define SZ(a) (int)((a).size())
#define ALL(a) (a).begin(),(a).end()
#define FLL(a,b) memset((a),b,sizeof(a))
#define CLR(a) memset((a),0,sizeof(a))
#define FOR(it,a) for(__typeof(a.begin())it=a.begin();it!=a.end();++it)
#define FORR(it,a) for(__typeof(a.rbegin())it=a.rbegin();it!=a.rend();++it)
template<typename T,typename U> ostream& operator<< (ostream& out, const pair<T,U>& val){return out << "(" << val.F << ", " << val.S << ")";}
template<class T> ostream& operator<< (ostream& out, const vector<T>& val){out << "{";rep(i,SZ(val)) out << (i?", ":"") << val[i];return out << "}";}
#define declare(a,it) __typeof(a) it=a
const double EPS = 1e-8;

const int dx[]={1,0,-1,0,1,1,-1,-1,0};
const int dy[]={0,1,0,-1,-1,1,-1,1,0};

const int MAX_P = 5100000;
bool npr[MAX_P];

int main(int argc, char *argv[])
{
  int n;
  cin >> n;
  vector<int> a(n);
  rep(i,n) cin >> a[i];
  int appa[10] = {};
  rep(i,n) appa[a[i]] = 1;
  
  npr[0] = npr[1] = 1;
  vector<int> app[10];
  int vis[10] = {};
  for(int i = 2; i < MAX_P; ++i){
    if(npr[i]) continue;
    int t = i;
    if(i<=5000000){
      while(t){
        int mo = t%10;
        if(vis[mo] != i)
          app[mo].pb(i);
        vis[mo] = i;
        t /= 10;
      }
    }
    for(int j = i*2; j < MAX_P; j += i)
      npr[j] = true;
  }

  //cerr << "hoge" << endl;
  
  int ans = -1;
  int lim = 5e6;
  for(int k = 1; k <= lim; ++k){
    int l =  lim;
    bool ok = true;
    rep(i,10){
      if(appa[i]) continue;
      auto it = lower_bound(ALL(app[i]),k);
      if(app[i].end() == it)
        continue;
      l = min(l, *it-1);
    }
    
    rep(i,10){
      if(!appa[i]) continue;
      auto it = upper_bound(ALL(app[i]),k-1);
      if(app[i].end() == it || *it > l){
        ok = false;
        break;
      }
    }
    
    if(ok){
      //cout << k << " " << l << endl;
      ans = max(ans, l - k);
    }
  }

  cout << ans << endl;
  
  return 0;
}