#include <fstream>
#include <vector>
#include <algorithm>
#include <iostream>

using namespace std;

class Task
{
  public:
	void solve()
	{
		read_input();
		aux.resize(caractere.size() + 1);
		print_output(get_result());
	}

  private:
	int n, k;
	string caractere;
	vector<int> freq;
	vector<char> aux;

	void read_input()
	{
		ifstream fin("in");
		fin >> n >> k;
		fin >> caractere;
		caractere = " " + caractere; // Adaugare element fictiv -
									 // indexare de la 1.
		freq.push_back(0);			 // Adaugare element fictiv - indexare de la 1.
		for (int i = 1, f; i <= n; i++)
		{
			fin >> f;
			freq.push_back(f);
			freq[0] += f; // Numarul total de caractere al sirului generat
		}
		fin.close();
	}

	void BKT(int p, vector<vector<char>> &sol)
	{
		for (int i = 1; i < caractere.size(); ++i)
		{
			if (freq[i])
			{
				int fr = k;
				for (int j = p - 1; j > 0 && fr > 0; --j)
				{
					if (aux[j] == caractere[i])
					{
						fr--;
					}
					else
					{
						break;
					}
				}
				if (fr == 0)
				{
					continue;
				}
				aux[p] = caractere[i];
				freq[i]--;
				freq[0]--;
				if (freq[0] == 0)
				{
					vector<char> s;
					for (int j = 1; j <= p; ++j)
					{
						s.push_back(aux[j]);
					}
					sol.push_back(s);
				}
				else
				{
					BKT(p + 1, sol);
				}
				freq[0]++;
				freq[i]++;
			}
		}
	}

	vector<vector<char>> get_result()
	{
		vector<vector<char>> all;

		BKT(1, all);

		return all;
	}

	void print_output(vector<vector<char>> result)
	{
		ofstream fout("out");
		fout << result.size() << '\n';
		for (int i = 0; i < (int)result.size(); i++)
		{
			for (int j = 0; j < (int)result[i].size(); j++)
			{
				fout << result[i][j];
			}
			fout << '\n';
		}
		fout.close();
	}
};

int main()
{
	Task task;
	task.solve();
	return 0;
}