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

template<typename T>
void chmax(T &a,T b){
  if(a<b)a=b;
}
vector<int> F[5000001];
int P[5000001];

bool prime(int a){
  if(a==1)return 0;
  if(~P[a])return P[a];
  for(int i=2;i*i<=a;i++)if(a%i==0)return P[a]=0;
  return P[a]=1;
}
vector<int> f(int a){
  if(F[a].size())return F[a];
  int tmp=a;
  vector<int> res;
  while(a){
    res.push_back(a%10);
    a/=10;
  }
  return F[tmp]=res;
}


signed main(){
  memset(P,-1,sizeof(P));
  int n;cin>>n;
  int ans=0;
  vector<int> v(10,0),now(10,0);
  while(n--){int a;cin>>a;v[a]++;}
  for(int l=1,r=1;r<=5000000;r++){
    if(prime(r)){
      for(int p:f(r))now[p]++;
      while(true){
        bool fl=false;
        for(int i=0;i<10;i++)if((!v[i])&&now[i])fl=1;
        if(fl){
          while(!prime(l))l++;
          for(int p:f(l))now[p]--;
          l++;
        }
        else break;
      }
    }
    int a=0;
    for(int i=0;i<10;i++)if((v[i]&&!now[i])||(!v[i]&&now[i]))a=1;
    if(!a)chmax(ans,r-l);
  }
  cout<<(ans?ans:-1)<<endl;
}