#include <cmath>
#include <functional>
#include <fstream>
#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <set>
#include <map>
#include <list>
#include <time.h>
#include <math.h>
#include <random>
#include <deque>
#include <cassert>
#include <queue>
#include <unordered_map>
#include <unordered_set>
#include <iomanip>
#include <bitset>
#include <sstream>
#include <stack>
#include <chrono>
#include <cstring>
#include <numeric>
using namespace std;
signed main() {
#ifndef INFOARENA
	FILE* stream;
	freopen_s(&stream, "input.txt", "r", stdin);
#else
	ios::sync_with_stdio(false);
	cin.tie(0);
	freopen("cuplaj.in", "r", stdin);
	freopen("cuplaj.out", "w", stdout);
#endif
	int dim1, dim2, edges;
	cin >> dim1 >> dim2 >> edges;
	vector<int> p1(dim1, -1), p2(dim2, -1);
	vector<vector<int>> g1(dim1);
	vector<bool> vis1(dim1, false);
	for (int i = 0; i < edges; i++) {
		int a, b;
		cin >> a >> b;
		a--, b--;
		assert(0 <= a && a < dim1);
		assert(0 <= b && b < dim2);
		g1[a].push_back(b);
	}
	function<bool(int)> dfs = [&](int a) {
		if (vis1[a]) {
			return false;
		}
		vis1[a] = true;
		for (auto& b : g1[a]) {
			if (p2[b] == -1) {
				p1[a] = b;
				p2[b] = a;
				return true;
			}
		}
		for (auto& b : g1[a]) {
			if (dfs(p2[b])) {
				p1[a] = b;
				p2[b] = a;
				return true;
			}
		}
		return false;
	};

	while (true) {
		bool changed = false;
		vis1.clear();
		vis1.resize(dim1, false);
		for (int i = 0; i < dim1; i++) {
			if (p1[i] == -1) {
				changed |= dfs(i);
			}
		}
		if (!changed) {
			break;
		}
	}
	int numpairs = 0;
	for (int i = 0; i < dim1; i++) {
		numpairs += (p1[i] != -1);
	}
	cout << numpairs << "\n";
	for (int i = 0; i < dim1; i++) {
		if (p1[i] != -1) {
			cout << i + 1 << " " << p1[i] + 1 << "\n";
		}
	}
	return 0;
}