#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef pair< int, int > pii;
typedef vector< int > vi;
typedef vector< vi > vvi;
typedef vector< ll > vl;
typedef vector< vl > vvl;
typedef vector< pii > vp;
typedef vector< vp > vvp;
typedef vector< string > vs;
typedef vector< double > vd;
typedef vector< vd > vvd;

template< class T1, class T2 >
int upmin( T1 &x, T2 v ){
  if( x > v ){
    x = v;
    return 1;
  }
  return 0;
}

template< class T1, class T2 >
int upmax( T1 &x, T2 v ){
  if( x < v ){
    x = v;
    return 1;
  }
  return 0;
}

int N;
vi A;

void init(){
  cin >> N;
  A = vi( N );
  for( int i = 0; i < N; ++i )
    cin >> A[ i ];
}

vi np;
vi ng;
vi ok;

void preprocess(){
  sort( A.begin(), A.end() );
  ng = vi( 10, 1 );
  for( int i = 0; i < A.size(); ++i )
    ng[ A[ i ] ] = 0;
  ok = vi( 10 );
  for( int i = 0; i < A.size(); ++i )
    ok[ A[ i ] ] = 1;
  np = vi( 5000001 + 1 );
  np[ 1 ] = 1;
  for( int i = 2; i < 5000001; ++i )
    if( not np[ i ] )
      for( int j = i + i; j < 5000001; j += i )
        np[ j ] = 1;
}

void solve(){
  int ans = -1;
  for( int i = 1; i <= 5000001; ++i ){
    set< int > dig;
    for( int j = i; j <= 5000001; ++j ){
      if( np[ j ] ) continue;
      int bad_flag = 0;
      for( int u = j; u; u /= 10 )
        if( ng[ u % 10 ] ){
          bad_flag = 1;
          break;
        }
      if( bad_flag or j == 5000001 ){
        int bad_bad_flag = 0;
        for( int k = 0; k < A.size(); ++k )
          if( not dig.count( A[ k ] ) )
            bad_bad_flag = 1;
        if( not bad_bad_flag )
          upmax( ans, j - 1 - i );
        i = j;
        break;
      }
      for( int u = j; u; u /= 10 )
        dig.emplace( u % 10 );
    }
  }
  cout << ans << endl;
}

signed main(){
  ios::sync_with_stdio( 0 );
  init();
  preprocess();
  solve();
  return 0;
}