#include<sstream>
#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<string>
#include<vector>
#include<set>
#include<map>
#include<queue>
#include<numeric>
#include<functional>
#include<algorithm>
using namespace std;
#define INF (1<<29)
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define all(v) v.begin(),v.end()
#define uniq(v) v.erase(unique(all(v)),v.end())
#define indexOf(v,x) (find(all(v),x)-v.begin())



//エラトステネスの篩 O(n loglog n)
#define MAX_N 5000000
int prime[MAX_N];//i番目の素数
bool is_prime[MAX_N+1];
int sieve(int n){
	int p=0;
	memset(is_prime,true,sizeof(is_prime));
	is_prime[0]=is_prime[1]=false;
	for(int i=2;i<=n;i++){
		if(is_prime[i]){
			prime[p++]=i;
			for(int j=2*i;j<=n;j+=i)is_prime[j]=false;
		}
	}
	return p;
}

int main(){
	int np=sieve(MAX_N);
	int n;
	bool a[10]={};
	cin>>n;
	rep(i,n){
		int m;
		cin>>m;
		a[m]=true;
	}
	int ans=-1;
	vector<int> idx;
	idx.push_back(-1);
	rep(i,np){
		bool ng=false;
		int m=prime[i];
		while(m){
			if(!a[m%10])ng=true;
			m/=10;
		}
		if(ng)idx.push_back(i);
	}
	idx.push_back(np);
	rep(i,idx.size()-1){
		bool used[10]={};
		int cnt=0;
		for(int j=idx[i]+1;j<idx[i+1];j++){
			int m=prime[j];
			while(m){
				if(a[m%10]&&!used[m%10]){used[m%10]=true;cnt++;}
				m/=10;
			}
		}
		int s=idx[i]==-1?0:prime[idx[i]];
		int e=idx[i+1]==np?MAX_N+1:prime[idx[i+1]];
		if(cnt==n)ans=max(ans,e-s-2);
	}
	cout<<ans<<endl;
	return 0;
}