#include <fstream>
#include <list>

using namespace std;

struct graph {

	int vertexCount;
	int edgeCount;
	int leftPart;
	list<int>* adjList;
	int* matchL;
	int* matchR;
	bool* viz;
	int matched = 0;
};

void readGraph(graph& g, ifstream& in) {
	int a, b;
	in >> a >> b >> g.edgeCount;
	g.vertexCount = a + b;
	g.leftPart = a;

	g.adjList = new list<int>[g.vertexCount + 1];

	for (int i = 1; i <= g.edgeCount; i++) {
		int v1, v2;
		in >> v1 >> v2;
		v2 += a;
		g.adjList[v1].push_back(v2);
	}

	g.matchL = (int*)calloc(g.vertexCount + 1, sizeof(int));
	g.matchR = (int*)calloc(g.vertexCount + 1, sizeof(int));
	g.viz = (bool*)calloc(g.vertexCount + 1, sizeof(bool));
}

bool findMatch(graph& g, int vertex) {

	if (g.viz[vertex])
		return false;
	g.viz[vertex] = true;



	for (auto adj : g.adjList[vertex]) {
		if (g.matchR[adj] == 0) {

			g.matchL[vertex] = adj;
			g.matchR[adj] = vertex;
			return true;
		}
	}

	for (auto adj : g.adjList[vertex]) {
		if (findMatch(g, g.matchR[adj])) {

			g.matchL[vertex] = adj;
			g.matchR[adj] = vertex;
			return true;
		}
	}


	return false;
}


int hopcroftKarp(graph& g) {

	bool changed = true;
	int maxMatching = 0;

	while (changed) {
		changed = false;

		for (int i = 1; i <= g.vertexCount; i++) g.viz[i] = false;

		for (int i = 1; i <= g.leftPart; i++)
			if (!g.matchL[i]) {

				bool matched = findMatch(g, i);
				changed |= matched;
			}

	}



	return g.matched;
}






int main() {

	graph g;

	ifstream in("cuplaj.in");
	readGraph(g, in);
	in.close();

	int maxMatching = hopcroftKarp(g);

	g.matched = 0;
	for (int i = 1; i <= g.leftPart; i++)
		if (g.matchL[i])
			g.matched++;

	ofstream out("cuplaj.out");
	out << g.matched << "\n";
	for (int i = 1; i <= g.leftPart; i++) {

		if (g.matchL[i])
			out << i << " " << g.matchL[i] - g.leftPart << "\n";
	}
	out.close();


	return 0;
}