#include <bits/stdc++.h>

using u32 = unsigned;
using i64 = long long;
using u64 = unsigned long long;

constexpr int N = 1E5 + 5;

int L, R, m, bel[N];
int vis[N];

std::vector<int> adj[N];

int dfs(int x, int i) {
	if (vis[x] == i) return 0;
	vis[x] = i;

	for (auto v : adj[x]) {
		if (!bel[v] || dfs(bel[v], i)) {
			bel[v] = x;
			return 1;
		}
	}

	return 0;
}

int main() {
	std::ios::sync_with_stdio(false);
	std::cin.tie(nullptr);

	std::cin >> L >> R >> m;

	for (int i = 1; i <= m; ++i) {
		int u, v;
		std::cin >> u >> v;
		++u, ++v;
		adj[u].push_back(v);
	}

	int ans = 0;
	
	for (int i = 1; i <= L; ++i) {
		ans += dfs(i, i);
	}

	std::cout << ans << "\n";

	for (int i = 1; i <= R; ++i) {
		if (bel[i]) std::cout << bel[i] - 1 << " " << i - 1 << "\n";
	}

	return 0;
}