#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
typedef long long int ll;
typedef long double ld;
#define FOR(i,l,r) for(ll i=l;i<r;i++)
#define REP(i,n) FOR(i,0,n)
#define RFOR(i,l,r) for(ll i=r-1;i>=l;i--)
#define RREP(i,n) RFOR(i,0,n)
#define ALL(x) x.begin(),x.end()
#define P pair<ll,ll>
#define F first
#define S second
#define BS(A,x) binary_search(ALL(A),x)
#define LB(A,x) (ll)(lower_bound(ALL(A),x)-A.begin())
#define UB(A,x) (ll)(upper_bound(ALL(A),x)-A.begin())
#define COU(A,x) UB(A,x)-LB(A,x)
template<typename T>using min_priority_queue=priority_queue<T,vector<T>,greater<T>>;
using mint=modint1000000007;
bool prime(ll N){ll d=2;while(d*d<=N){if(N%d==0)return 0;d++;}return 1;}
signed main(){
  ll N,ans=-1;cin>>N;vector<bool>X(10,0),p(5000001,1);REP(i,N){ll A;cin>>A;X[A]=1;}
  p[0]=0;p[1]=0;FOR(i,2,5000001){ll j=2*i;while(j<=5000000){p[j]=0;j+=i;}}
  vector<ll>PRIME;PRIME.push_back(0);REP(i,5000001)if(p[i])PRIME.push_back(i);
  PRIME.push_back(5000001);vector<ll>DP(10,0);ll r=1;
  FOR(i,1,PRIME.size()-1){
    bool x=0;r=max(r,i);
    while(r<PRIME.size()-1){
      ll k=PRIME[r];while(k){if(!X[k%10])x=1;k/=10;}if(x)break;
      k=PRIME[r];while(k){DP[k%10]++;k/=10;}r++;
    }
    if(i<r){
      bool x=1;REP(j,10)if(X[j]&&DP[j]==0)x=0;
      if(x)ans=max(ans,PRIME[r]-2-PRIME[i-1]);
      ll k=PRIME[i];while(k){DP[k%10]--;k/=10;}
    }
    else REP(j,10)DP[j]=0;
  }
  cout<<ans<<endl;
  return 0;
}