//Author: Kevin5307
#include<bits/stdc++.h>
//#pragma GCC optimize("O2")
using namespace std;
#define ll long long
#define ull unsigned ll
#define pb emplace_back
#define mp make_pair
#define ALL(x) (x).begin(),(x).end()
#define rALL(x) (x).rbegin(),(x).rend()
#define srt(x) sort(ALL(x))
#define rev(x) reverse(ALL(x))
#define rsrt(x) sort(rALL(x))
#define sz(x) (int)(x.size())
#define inf 0x3f3f3f3f
#define pii pair<int,int>
#define lb(v,x) (int)(lower_bound(ALL(v),x)-v.begin())
#define ub(v,x) (int)(upper_bound(ALL(v),x)-v.begin())
#define uni(v) v.resize(unique(ALL(v))-v.begin())
#define longer __int128_t
void die(string S){puts(S.c_str());exit(0);}
bool flag[15];
bool check(int x)
{
	while(x)
	{
		if(flag[x%10]) return false;
		x/=10;
	}
	return true;
}
bool prime[1001000];
int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	int k;
	cin>>k;
	while(k--)
	{
		int x;
		cin>>x;
		flag[x]=1;
	}
	for(int i=2;i<1001000;i++)
		for(int j=i+i;j<1001000;j+=i)
			prime[j]=1;
	for(int i=2;i<1001000;i++)
		if(!prime[i]&&check(i))
		{
			cout<<i<<endl;
			return 0;
		}
	cout<<-1<<endl;
	return 0;
}