#include <iostream>
#include <cstdio>
#include <vector>
#include <queue>
using namespace std;

vector<vector<int>> al;
vector<int> mt;
vector<bool> vis;
queue<int> q;

int main() {
#ifdef INFOARENA
	freopen("cuplaj.in", "r", stdin);
	freopen("cuplaj.out", "w", stdout);
#endif
	cin.sync_with_stdio(false);
	int n0, n1, m;
	cin >> n0 >> n1 >> m;
	al.resize(n0);
	mt.assign(n0+n1, -1);
	for (int u, v, i = 0; i < m; i++) {
		cin >> u >> v;
		u--;
		v += n0-1;
		al[u].push_back(v);
	}
	int nm = 0;
	bool chg;
	vector<int> p(n0);
	do {
		chg = false;
		vis.assign(n0, false);
		for (int u = 0; u < n0; u++) {
			if (mt[u] == -1) {
				q.push(u);
				vis[u] = true;
			}
		}
		while (!q.empty()) {
			int u = q.front();
			q.pop();
			for (int v: al[u]) {
				if (mt[v] == -1) {
					do {
						mt[v] = u;
						int v1 = mt[u];
						mt[u] = v;
						u = p[u];
						v = v1;
					} while (v != -1);
					nm++;
					chg = true;
					break;
				} else if (!vis[mt[v]]) {
					q.push(mt[v]);
					vis[mt[v]] = true;
					p[mt[v]] = u;
				}
			}
		}
	} while (chg);
	printf("%d\n", nm);
	for (int u = 0; u < n0; u++) {
		if (mt[u] != -1)
			printf("%d %d\n", u+1, mt[u]-n0+1);
	}
	return 0;
}