#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;

typedef long long ll;
typedef unsigned long long ull;

static const double EPS = 1e-8;
static const double PI = 4.0 * atan(1.0);
static const double PI2 = 8.0 * atan(1.0);

#define REP(i,n)	for(int i=0;i<(int)n;++i)
#define ALL(c)		(c).begin(),(c).end()
#define CLEAR(v)	memset(v,0,sizeof(v))
#define MP(a,b)		make_pair((a),(b))
#define ABS(a)		((a)>0?(a):-(a))
#define FOR(i,s,n)	for(int i=s;i<(int)n;++i)

int N;
int A;

bool np[5000001];
vector<int> primes;
const int n = 1 << 19;
int seg[2 * n - 1];

int h(int n) {
	int res = 0;
	while (n > 0) {
		res |= 1 << (n % 10);
		n /= 10;
	}
	return res;
}

void update(int k, int a) {
	k += n - 1;
	seg[k] = a;
	while (k > 0) {
		k = (k - 1) / 2;
		seg[k] = seg[k * 2 + 1] | seg[k * 2 + 2];
	}
}

int query(int a, int b, int k, int l, int r) {
	if (r <= a || b <= l) return 0;
	if (a <= l && r <= b) return seg[k];
	int vl = query(a, b, k * 2 + 1, l, (l + r) / 2);
	int vr = query(a, b, k * 2 + 2, (l + r) / 2, r);
	return vl | vr;
}

int main(int argc, char **argv) {
	cin >> N;
	A = 0;
	REP(i, N) {
		int t; cin >> t;
		A |= (1 << t);
	}

	CLEAR(np);
	np[0] = np[1] = true;
	FOR(i, 2, 5000001) {
		if (np[i]) continue;
		primes.push_back(i);
		for (int j = i * 2; j < 5000001; j += i) np[j] = true;
	}
	int pc = primes.size();

	REP(i, n) seg[i] = 0;
	REP(i, pc) update(i, h(primes[i]));

	int l = 0, r = 0;
	int res = 0;
	while (l < pc && r < pc) {
		int v = query(l, r + 1, 0, 0, n);
		if ((v & (~A)) != 0) {
			++l;
			if (l > r) ++r;
		}
		else {
			if (v == A) {
				int lp = l == 0 ? 1 : primes[l - 1] + 1;
				int rp = r == pc - 1 ? 5000000 : primes[r + 1] - 1;
				res = max(res, rp - lp);
			}
			++r;
		}
	}

	cout << (res == 0 ? -1 : res) << endl;
	return 0;
}