#pragma GCC optimize ("O3")
#pragma GCC target ("avx")
#include "bits/stdc++.h" // define macro "/D__MAI"

using namespace std;
typedef long long int ll;

#define debugv(v) {printf("L%d %s => ",__LINE__,#v);for(auto e:v){cout<<e<<" ";}cout<<endl;}
#define debugm(m) {printf("L%d %s is..\n",__LINE__,#m);for(auto v:m){for(auto e:v){cout<<e<<" ";}cout<<endl;}}
#define debuga(m,w) {printf("L%d %s is => ",__LINE__,#m);for(int x=0;x<(w);x++){cout<<(m)[x]<<" ";}cout<<endl;}}
#define debugaa(m,w,h) {printf("L%d %s is..\n",__LINE__,#m);for(int y=0;y<(h);y++){for(int x=0;x<(w);x++){cout<<(m)[x][y]<<" ";}cout<<endl;}}
#define debugaar(m,w,h) {printf("L%d %s is..\n",__LINE__,#m);for(int y=0;y<(h);y++){for(int x=0;x<(w);x++){cout<<(m)[y][x]<<" ";}cout<<endl;}}
#define ALL(v) (v).begin(),(v).end()
#define repeat(l) for(auto cnt=0;cnt<(l);++cnt)
#define iterate(b,e) for(auto cnt=(b);cnt!=(e);++cnt)
#define MD 1000000007ll
#define PI 3.1415926535897932384626433832795
template<typename T1, typename T2>
ostream& operator <<(ostream &o, const pair<T1, T2> p) { o << "(" << p.first << ":" << p.second << ")"; return o; }

mt19937 mt(8901016);
inline int rand_int(int l, int h) {
    return uniform_int_distribution<>(l, h)(mt);
}

#ifdef __MAI
#define getchar_unlocked getchar
#define putchar_unlocked putchar
#endif
#ifdef __VSCC
#define getchar_unlocked _getchar_nolock
#define putchar_unlocked _putchar_nolock
#endif
namespace {
#define isvisiablechar(c) (0x21<=(c)&&(c)<=0x7E)
    class MaiScanner {
    public:
        template<typename T> void input_integer(T& var) {
            var = 0;
            T sign = 1;
            int cc = getchar_unlocked();
            for (; cc<'0' || '9'<cc; cc = getchar_unlocked())
                if (cc == '-') sign = -1;
            for (; '0' <= cc&&cc <= '9'; cc = getchar_unlocked())
                var = (var << 3) + (var << 1) + cc - '0';
            var = var*sign;
        }
        inline int c() { return getchar_unlocked(); }
        inline MaiScanner& operator>>(int& var) {
            input_integer<int>(var);
            return *this;
        }
        inline MaiScanner& operator>>(long long& var) {
            input_integer<long long>(var);
            return *this;
        }
        inline MaiScanner& operator>>(string& var) {
            int cc = getchar_unlocked();
            for (; !isvisiablechar(cc); cc = getchar_unlocked());
            for (; isvisiablechar(cc); cc = getchar_unlocked())
                var.push_back(cc);
        }
        template<typename IT> void in(IT begin, IT end){
            for (auto it = begin; it != end; ++it) *this >> *it;
        }
    };
}
MaiScanner scanner;



void gen_primelist(vector<ll>& out, int high) {
    out.resize(high + 1);
    out[0] = out[1] = 1;
    ll sqh = (ll)sqrt(high);
    for (ll i = 2; i <= sqh; i++) {
        if (out[i] == 0) {
            for (ll j = i*i; j <= high; j += i) { // i*i
                out[j] = 1;
            }
        }
    }
}



int m, n, kei;

int main() {
    vector<int> aa(10);
    vector<int> bb(10);

    scanner >> n;
    repeat(n) {
        int a;
        scanner >> a;
        aa[a] = 1;
    }

    vector<ll> isprime;
    gen_primelist(isprime, 5000004);

    ll left = 2;
    ll best = -1;

    int status = 0;
    for (ll val = 2; val < 5000004; ++val) {
        if (status == 1){
            best = max(best, val - left - 2);
        }
        
        if (isprime[val]) continue;

        function<void(ll)> lf_add = [&](ll z) {
            bb[z%10] += 1;
            if (z >= 10) lf_add(z / 10);
            return ;
        };
        lf_add(val);

        status = 1;
        for (int i = 0; i < 10; ++i) {
            if (!aa[i] && !!bb[i]) {
                // はずれ
                status = -1; break;
            }
            status &= !aa[i] || !!bb[i];
        }
        if (status == -1) {
            left = val;
            fill(ALL(bb), 0);
        }
        else if (status == 1) {
            best = max(best, val - left);
        }
    }

    cout << best << endl;

    return 0;
}