/*For today, you happen to be the defeated. But what will you become tomorrow?*/

#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace __gnu_pbds;
using namespace std;

#define int long long int 
#define dbg if(debugg)
#define F first 
#define S second 

bool debugg = false;

template <typename T>
using order_set = tree<T, null_type,less<T>, rb_tree_tag,tree_order_statistics_node_update>;

template <typename T>
using minheap = priority_queue<T, vector<T>, greater<T>>;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());  

int ok[10];
bool prime(int n)
{
	for(int i = 2; i * i <= n; i ++){
		if(n % i == 0) return 0;
	}
	return 1;
}

bool f(int n)
{
	while(n > 0){
		if(ok[n % 10]) return 0;
		n /= 10;
	}
	return 1;
}
void solve()
{
	int n;
	cin >> n;
	for(int i = 0; i < n; i ++){
		int a;
		cin >> a;
		ok[a] = 1;
	}

	for(int i = 2; i < 1000; i ++){
		if(prime(i) && f(i)){
			cout << i << '\n';
			return;
		}
	}
	cout << -1 << '\n';
}

int32_t main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
        
    int t = 1;
    // cin >> t;
    
    while(t--){
        solve();
    }

    return 0;
}