#include "bits/stdc++.h"
using namespace std;

typedef long long Int;
#define REP(i,n) for(int (i)=0;(i)<(int)(n);++(i))

const int MAX_N = 5000000;
bool is_prime[MAX_N];
vector<int> primes;

vector<int> dis(int p) {
	vector<int> res(10);
	while (p > 0) {
		res[p % 10]++;
		p /= 10;
	}
	return res;
}

int main() {
	for (int i = 0; i < MAX_N; i++) is_prime[i] = true;
	is_prime[0] = is_prime[1] = false;
	for (int i = 2; i * i <= MAX_N; i++)
		if (is_prime[i])
			for (int j = i * i; j < MAX_N; j += i)
				is_prime[j] = false;

	primes.push_back(0);
	for (int i = 0; i < MAX_N; i++) {
		if (is_prime[i]) primes.push_back(i);
	}
	primes.push_back(5000001);

	vector<int> target(10);
	int N; cin >> N; REP(i, N) { int x; cin >> x; target[x]++; }
	vector<int> current(10);
	int left = 1, right = 1;
	int ans = -1;
	int LIM = primes.size() - 1;
	while (right < LIM || left < LIM) {
		bool fast = false;
		bool slow = false;
		REP(i, 10) {
			if (current[i] > 0 && target[i] == 0) fast = true;
			if (current[i] == 0 && target[i] > 0) slow = true;
		}

		if (!fast && !slow) {
			ans = max(ans, (primes[right] - 1) - (primes[left-1] + 1));
		}

		if (right >= LIM || fast) {
			vector<int> v = dis(primes[left]);
			REP(i, 10) current[i] -= v[i];
			left++;
		}
		else {
			vector<int> v = dis(primes[right]);
			REP(i, 10) current[i] += v[i];
			right++;
		}

	}
	cout << ans << endl;
}