#include <algorithm>
#include <cstdio>
#include <cstdlib>
#include <cctype>
#include <cmath>
#include <iostream>
#include <queue>
#include <list>
#include <map>
#include <numeric>
#include <set>
#include <sstream>
#include <string>
#include <vector>
using namespace std;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;

#define MAX_PRIME 5000000
bool isprime[MAX_PRIME+1]; 
vector<int> primes; 
void init_prime(){
  fill(isprime, isprime+MAX_PRIME+1, true); 
  isprime[0] = isprime[1] = false; 
  for(int i = 2; i <= MAX_PRIME; i++) { 
    if (isprime[i]) { 
      primes.push_back(i); 
      for(int j = i*2; j <= MAX_PRIME; j += i) 
        isprime[j] = false; 
    } 
  } 
}

int bits[MAX_PRIME+1];

int main(){
  init_prime();
  
  int N, a, ans = 0;

  cin >> N;
  rep(i,N){
    cin >> a;
    ans |= 1<<a;
  }

  rep(i,primes.size()){
    int x = primes[i];
    int res = 0;
    while(x>0){
      res |= 1<<(x%10);
      x /= 10;
    }
    bits[primes[i]] = res;
  }
  
  vector<int> flg(primes.size(), 0);
  rep(i,primes.size()){
    if((bits[primes[i]]|ans) == ans){
      flg[i] = 1;
    }
  }

  int ret = -1;
  for(int i=0; i<primes.size();){
    if(flg[i]==1){
      int bgn = i, end;
      int res = 0;
      while(flg[i]==1){
        res |= bits[primes[i]];
        i++;
      }
      end = i;
      if(res == ans){

        if(bgn==0) bgn = 1;
        else bgn = primes[bgn-1]+1;
        if(end==primes.size()) end = 5000000;
        else end = primes[i]-1;
        
        ret = max(ret, end-bgn);
      }
    }else{
      i++;
    }
  }

  cout << ret << endl;
  
  return 0;
}