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

using namespace std;

long N, K;

typedef class task {
	public:
		long S;
		string name;
		bool operator< (const task& rhs) const {
			return S < rhs.S;
		}
} task;

typedef class blockchain {
	public:
		long k;
		vector<task> T;
		blockchain () {}
		blockchain (long _k) : k(_k), T(vector<task> ()) {}
		bool operator< (const blockchain& rhs) const{
			return k < rhs.k;
		}
} blockchain;

inline char inc (char in)
{
	return ((in - 65 + K) % 26) + 65;
}

int main ()
{
	cin.tie (0);
	ios_base::sync_with_stdio (false);

	//ifstream cin("uzduotys.in");

	cin >> N >> K;

	auto T = vector<task> (N);
	for (long i = 0; i < N; i++)
	{
		cin >> T[i].name >> T[i].S;
	}

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

	auto M = map<char, multimap<long, blockchain> > ();
	for (long i = 0; i < K; i++)
	{
		char c = 65 + (i % 26);
		M[c].insert (make_pair (0, blockchain (i)));
	}

	for (auto& item : T)
	{
		auto& c = M[item.name[0]];
		auto it = c.begin ();
		if (it != c.end ())
		{
			auto& vec = it->second.T;
			if (vec.empty() || vec[vec.size() - 1].S < item.S)
			{
				vec.push_back (item);
				M[inc (item.name[0])].insert (make_pair (vec.size (), it->second));

				c.erase (it);
			}
		}
	}

	auto V = vector<blockchain*> (K);

	pair<long, long> mini;
	bool found = false;
	for (auto& it : M)
	{
		for (auto& el : it.second)
		{
			V[el.second.k] = &el.second;
			auto tmp = make_pair(el.first, el.second.k);
			if (found == false || mini > tmp)
			{
				mini = tmp;
				found = true;
			}
		}
	}

	cout << K * mini.first + mini.second << '\n';
	for (long i = 0; i < mini.first; i++)
	{
		for (long j = 0; j < K; j++)
		{
			cout << V[j]->T[i].name << '\n';
		}
	}
	for (long i = 0; i < mini.second; i++)
	{
		cout << V[i]->T[mini.first].name << '\n';
	}
	//cin.close ();
}