#line 2 "header.hpp"

//%snippet.set('header')%
//%snippet.fold()%
#ifndef HEADER_H
#define HEADER_H

// template version 2.0
using namespace std;
#include <bits/stdc++.h>

// varibable settings
const long long INF = 1e18;
template <class T> constexpr T inf = numeric_limits<T>::max() / 2.1;

#define _overload3(_1, _2, _3, name, ...) name
#define _rep(i, n) repi(i, 0, n)
#define repi(i, a, b) for (ll i = (ll)(a); i < (ll)(b); ++i)
#define rep(...) _overload3(__VA_ARGS__, repi, _rep, )(__VA_ARGS__)
#define _rrep(i, n) rrepi(i, 0, n)
#define rrepi(i, a, b) for (ll i = (ll)((b)-1); i >= (ll)(a); --i)
#define r_rep(...) _overload3(__VA_ARGS__, rrepi, _rrep, )(__VA_ARGS__)
#define each(i, a) for (auto &&i : a)
#define all(x) (x).begin(), (x).end()
#define sz(x) ((int)(x).size())
#define pb(a) push_back(a)
#define mp(a, b) make_pair(a, b)
#define mt(...) make_tuple(__VA_ARGS__)
#define ub upper_bound
#define lb lower_bound
#define lpos(A, x) (lower_bound(all(A), x) - A.begin())
#define upos(A, x) (upper_bound(all(A), x) - A.begin())
template <class T> inline void chmax(T &a, const T &b) { if ((a) < (b)) (a) = (b); }
template <class T> inline void chmin(T &a, const T &b) { if ((a) > (b)) (a) = (b); }
template <typename X, typename T> auto make_table(X x, T a) { return vector<T>(x, a); }
template <typename X, typename Y, typename Z, typename... Zs> auto make_table(X x, Y y, Z z, Zs... zs) { auto cont = make_table(y, z, zs...); return vector<decltype(cont)>(x, cont); }

#define divceil(a, b) ((a) + (b)-1) / (b)
#define is_in(x, a, b) ((a) <= (x) && (x) < (b))
#define uni(x) sort(all(x)); x.erase(unique(all(x)), x.end())
#define slice(l, r) substr(l, r - l)

typedef long long ll;
typedef long double ld;
using vl = vector<ll>;
using vvl = vector<vl>;
using pll = pair<ll, ll>;

template <typename T>
using PQ = priority_queue<T, vector<T>, greater<T>>;
void check_input() { assert(cin.eof() == 0); int tmp; cin >> tmp; assert(cin.eof() == 1); }

#if defined(PCM) || defined(LOCAL)
#else
#define dump(...) ;
#define dump_1d(...) ;
#define dump_2d(...) ;
#define cerrendl ;
#endif

#endif /* HEADER_H */
//%snippet.end()%
#line 2 "solve.cpp"
template<class T=ll> using vec = vector<T>;
struct Fast { Fast() { std::cin.tie(0); ios::sync_with_stdio(false); } } fast;

// snippet:sieve {{{
struct Sieve {/*{{{*/
    // エラトステネスのふるい O(NloglogN)
    int n;                              // n
    vector<int> f;                      // [1, 2, 3, 2, 5, 2, 7, 2, 3, ....]
    vector<int> primes;                 // [2, 3, 5, .......]
    Sieve(int n = 1) : n(n), f(n + 1) { /*{{{*/
        f[0] = f[1] = -1;
        for (ll i = 2; i <= n; ++i) {
            if (f[i]) continue;
            primes.push_back(i);
            f[i] = i;
            for (ll j = i * i; j <= n; j += i) {
                if (!f[j]) f[j] = i;
            }
        }
    } /*}}}*/
    bool is_prime(int x) { return f[x] == x; }

    vector<int> factor_list(int x) { /*{{{*/
        // n**2くらいまでは計算できるはず
        vector<int> res;
        if (x < n) {
            while (x != 1) {
                res.push_back(f[x]);
                x /= f[x];
            }
        }
        else {
            for (int i = 0; primes[i] * primes[i] <= x; i++) {
                while (x % primes[i] == 0) {
                    res.pb(primes[i]);
                    x /= primes[i];
                }
            }
            if (x != 1) res.pb(x);
        }

        return res;  // [2, 3, 3, 5, 5, 5.....]
    }                /*}}}*/

    vector<pair<int, int>> factor(int x) { /*{{{*/
        vector<int> fl = factor_list(x);
        if (fl.size() == 0) return {};
        vector<pair<int, int>> res(1, mp(fl[0], 0));
        for (int p : fl) {
            if (res.back().first == p) {
                res.back().second++;
            } else {
                res.emplace_back(p, 1);
            }
        }
        return res;  // [(2,1), (3,2), (5,3), .....]
    }                /*}}}*/
};/*}}}*/
Sieve sv(5e6+1);
// How to use
// sv.primes      // 素数のリスト
// sv.factor(x);  // 素因数分解
// snippet:sieve }}}

string to_bin(ll n, ll d = 10){/*{{{*/
    // nをd桁の2進数で表示する。
    stringstream ss;
    ss << bitset<64>(n);
    return ss.str().substr(64-d, d);
}/*}}}*/
// ll d = (32 - __builtin_clz(n));  // 最大桁のd: (2^d)
// ll f = N - d; to_bin()で返ってきた文字列で最初に1が立っているindex

int solve() {
    ll n;cin>>n;
    dump(n);
    vector<ll> a(n);
    ll s1 = 0;
    rep(i, n) {
        cin>>a[i];
        dump(i, a[i]);
        s1 |= 1<<a[i];
        dump(to_bin(s1));
        dump(s1);
    }
    dump(a);
    dump(to_bin(s1));

    // const int V = 10;
    const int V = 5000000;
    vvl x(V+1);
    rep(i, 1, V+1){
        if (sv.is_prime(i)){
            ll ii = i;
            while(ii>0){
                x[i].pb(ii % 10);
                ii /= 10;
            }
        }
    }
    // dump(x);

    const ll R = V+1;
    ll sum = 0;
    auto isok = [&](ll next_r) {  // check [l, next_r) is ok?
        ll nsum = sum;
        each(el, x[next_r-1]){
            nsum |= 1LL<<el;
        }
        dump(to_bin(nsum));
        if ((nsum & s1) == nsum)
            return true;
        else
            return false;
    };

    ll res = -1;
    ll r = 1;
    for (ll l = 1; l < R; ++l) {
        // [l, r)を限界まで広げる。
        while (r < R && isok(r + 1)) {
            each(el, x[r]){
                sum |= 1LL<<el;
            }
            ++r;
        }
        dump(l, r);
        dump(to_bin(sum));
        if (sum == s1) chmax(res, (r - l - 1));

        // leftをincrementする準備
        if (r == l)
            ++r;  // 空区間から空区間への変動なので何もしない。
        else{
            each(el, x[l]){
                sum &= ~(1LL<<el);
            }
        }
    }
    cout << res << endl;

    return 0; 
}


int main(){/*{{{*/
    solve();
    check_input();
    return 0;
}/*}}}*/