// password.cpp : Defines the entry point for the console application.
//

#include <fstream>
#include <string>
#include <vector>

using namespace std;
int main(int argc, char* argv[])
{
    int N;
    string str;
    str.reserve(100000);
    fstream fin, fout;
    fin.open("password.in", ios_base::in);
    fin >> N;
    fin >> str;

    fout.open("password.out", ios_base::out);
    if (N == 1)
    {
        fout << 1 << endl;
        fout << str << endl;
    }
    else
    {
        vector<string> passwords;
        passwords.reserve(100000);
        int max = 1, last = 1;
        for (int i = 1; i < N; i++)
        {
            if (str[i] == str[i - 1])
            {
                max++;
            }
            else
            {
                if (max > last)
                {
                    passwords.clear();
                    last = max;
                }
                if (max == last)
                {
                    passwords.push_back(str.substr(i - max, max));
                    last = max;
                }
                max = 1;
            }
        }
        if (max > last)
        {
            passwords.clear();
            last = max;
        }
        if (max == last)
        {
            passwords.push_back(str.substr(N - max, max));
            last = max;
        }
        fout << passwords.size() << endl;
        for (int i = 0; i < passwords.size(); i++)
            fout << passwords[i] << endl;
    }

	return 0;
}