#include <fstream>
#include <algorithm>
#include <vector>
using namespace std;

static bool try_to_repair(const int x, const vector<vector<int>>& graf, vector<int>& right, vector<int>& left, vector<bool>& used){
	if(used[x]){
		return false; }
	used[x] = true;
	for(const auto y : graf[x]){
		if(left[y] == -1){
			right[x] = y;
			left[y] = x;
			return true; } }
	for(const auto y : graf[x]){
		if(try_to_repair(left[y], graf, right, left, used)){
			right[x] = y;
			left[y] = x;
			return true; } }
	return false; }

int main(){
	ifstream f("cuplaj.in");
	ofstream g("cuplaj.out");
	int n, m, e;

	f >> n >> m >> e;

	static vector<vector<int>> graf(n);
	for(int i = 0, a, b; i < e; ++i){
		f >> a >> b;
		graf[a-1].push_back(b-1); }

	static vector<int> right(n, -1), left(m, -1);
	static vector<bool> used(n, false);

	for(bool changed = true; changed; ){
		changed = false;
		fill(begin(used), end(used), false);
		for(int i = 0; i < n; ++i){
			if(right[i] == -1){
				changed = changed || try_to_repair(i, graf, right, left, used); } } }

	const int sz_cuplaj = count_if(begin(right), end(right), [](const int x){ return x != -1; });
	g << sz_cuplaj << endl;
	for(int i = 0; i < n; ++i){
		if(right[i] != -1){
			g << i+1 << ' ' << right[i]+1 << endl; } }

	return 0; }