#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <queue>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>

using namespace std;

inline int toInt(string s) {int v; istringstream sin(s);sin>>v;return v;}
template<class T> inline string toString(T x) {ostringstream sout;sout<<x;return sout.str();}

typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;
typedef unsigned long long ULL;

#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)  FOR(i,0,n)

#define MP make_pair
#define SZ(a) int((a).size())
#define EACH(i,c) for(auto i: c)
#define EXIST(s,e) (find((s).begin(), (s).end(), (e))!=(s).end())
#define SORT(c) sort((c).begin(),(c).end())

const double EPS = 1e-10;
const double PI  = acos(-1.0);

#define dump(x)  cerr << #x << " = " << (x) << endl;
#define debug(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);

	int N;
	cin >> N;
	set<int> A;
	REP(i, N){
		int tmp;
		cin >> tmp;
		A.insert(tmp);
	}

	function<bool(int)> f = [=](int n){
		while(n != 0){
			if(EXIST(A, n % 10)) n /= 10;
			else return false;
		}
		return true;
	};

	const int MAX = 5000001;
	int ret = -1, preNum = 0;
	bool ok = false;
	set<int> B;
	vector<bool> isPrime(MAX, true);
	isPrime[0] = isPrime[1] = false;
	REP(i, MAX){
		if(isPrime[i]){
			for(int j = i; j <= MAX; j += i) isPrime[j] = false;
			if(f(i)){
				int x = i;
				while(x != 0){
					B.insert(x % 10);
					x /= 10;
				}
				ok = true;
			}
			else{
				if(ok && A.size() == B.size()) ret = max(ret, i - preNum - 1);
				preNum = i + 1;
				ok = false;
				B.clear();
			}
		}
		else{
			if(ok && A.size() == B.size()) ret = max(ret, i - preNum - 1);
		}

	}


	cout << ret << endl;


	return 0;
}