#include <algorithm>
#include <iostream>
#include <cstdio>
#include <map>
#include <numeric>
#include <cmath>
#include <set>
#include <sstream>
#include <string>
#include <vector>
#include <queue>
#include <complex>
#include <string.h>
#include <unordered_set>
#include <unordered_map>
using namespace std;

#define endl '\n'
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define uniq(v) (v).erase(unique((v).begin(), (v).end()), (v).end())

typedef long long ll;
typedef pair<int, int> P;
typedef unsigned int uint;
typedef unsigned long long ull;
struct pairhash {
public:
    template<typename T, typename U>
    size_t operator()(const pair<T, U> &x) const {
	size_t seed = hash<T>()(x.first);
	return hash<U>()(x.second) + 0x9e3779b9 + (seed<<6) + (seed>>2);
    }
};

const int inf = 1000000009;
bool is_prime[5000009];
vector<int> primes;
void sieve(int n) {
    memset(is_prime, true, sizeof(is_prime));
    is_prime[0] = is_prime[1] = false;
    for (int i = 2; i <= n; i++) {
	if (is_prime[i]) {
	    primes.push_back(i);
	    for (int j = i + i; j <= n; j += i)
		is_prime[j] = false;
	}
    }
}
vector<bool> as(10, false);
vector<bool> used(10, false);
bool check(int n) {
    int m = n;
    while (n > 0) {
	int k = n % 10;
	if (!as[k]) return false;
	n /= 10;
    }
    while (m > 0) {
	int k = m % 10;
	used[k] = true;
	m /= 10;
    }
    return true;
}

bool sat() {
    for (int i = 0; i < 10; i++)
	if (as[i] != used[i])
	    return false;
    return true;
}

int solve(int n) {
    sieve(5000000);
    for (int i = 0; i < n; i++) {
	int a;
	scanf("%d", &a);
	as[a] = true;
    }

    int len = primes.size();
    int l = 1, res = -1;
    for (int i = 0; i < len; i++) {
	if (!check(primes[i])) {
	    if (sat()) {
		res = max(res, primes[i]-1-l);
	    }
	    l = primes[i] + 1;
	    for (int j = 0; j < 10; j++) used[j] = false;
	}
    }
    if (sat())
	res = max(res, 5000000-l);
    return (res > 0 ? res : -1);
}

int main() {
    int n;
    scanf("%d", &n);
    printf("%d\n", solve(n));
}