#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 <queue>
#include <unordered_map>
#include <unordered_set>
#include <iomanip>
#include <cassert>
#include <bitset>
#include <sstream>
#include <chrono>
#include <cstring>
#include <numeric>

using namespace std;

signed main() {
#ifdef INFOARENA
	freopen("cuplaj.in", "r", stdin);
	freopen("cuplaj.out", "w", stdout);

	ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#else
	FILE* stream;
	freopen_s(&stream, "input.txt", "r", stdin);
#endif

	int n, m, e;
	cin >> n >> m >> e;
	vector<int> l(n, -1), r(m, -1);
	vector<bool> vis(n);
	vector<vector<int>> g(n);
	for (int i = 0; i < e; i++) {
		int a, b;
		cin >> a >> b;
		a--;
		b--;
		assert(0 <= a && a < n);
		assert(0 <= b && b < m);
		g[a].push_back(b);
	}

	function<bool(int)> dfs = [&](int a) {
		if (vis[a]) return 0;
		vis[a] = 1;
		for (auto& b : g[a]) if (r[b] == -1) {
			l[a] = b, r[b] = a;
			return 1;
		}
		for (auto& b : g[a]) if (dfs(r[b])) {
			l[a] = b, r[b] = a;
			return 1;
		}
		return 0;
	};

	for (int _ = 1; _--; ) {
		vis.clear();
		vis.resize(n, 0);
		for (int i = 0; i < n; i++) if (l[i] == -1) _ |= dfs(i);
	}
	int cnt = 0;
	for (int i = 0; i < n; i++) cnt += (l[i] != -1);
	cout << cnt << "\n";
	for (int i = 0; i < n; i++) if (l[i] != -1) cout << 1 + i << " " << 1 + l[i] << "\n";

	return 0;
}