#include <bits/stdc++.h>
#define ONLINE_JUDGE
using namespace std;

int n;
string s;
vector<string> passwords;

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    passwords.clear();
    #ifdef ONLINE_JUDGE
    freopen("password.in", "r", stdin);
    freopen("password.out", "w", stdout);
    #endif // ONLINE_JUDGE

    cin >> n;
    cin >> s;

    int i, j;
    int ml = 1, curl = 1;
    int br[10];
    string pass;

    memset(br, 0, sizeof(br));

    for (i = 0; i < n - 1; i++)
    {
        br[s[i] - '0']++;
        if (s[i] == s[i + 1]) curl++;
        else
        {
            if (curl > ml)
            {
                ml = curl;
                curl = 1;
            }
        }
    }
    br[s[s.size() - 1] - '0']++;

    if (curl > ml) ml = curl;

    for (i = 0; i < 10; i++)
    {
        if (br[i] == ml)
        {
            pass = "";
            for (j = 0; j < ml; j++)
            {
                pass = pass + char(i + '0');
            }
            passwords.push_back(pass);
        }
    }

    sort(passwords.begin(), passwords.end());

    cout << passwords.size() << '\n';
    for (i = 0; i < passwords.size(); i++)
    {
        cout << passwords[i] << '\n';
    }

    return 0;
}