#include <bits/stdc++.h>
using namespace std;
using i64 = long long;

int main() {
  cin.tie(nullptr)->sync_with_stdio(false);
  int l, r, m;
  cin >> l >> r >> m;
  vector < vector < int > > g(l);
  for (int i = 1, u, v; i <= m; i++) {
    cin >> u >> v;
    g[u].push_back(v);
  }
  vector < int > mch(r, -1), vis(r, -1);
  auto dfs = [&](auto &self, int u, int t) -> int {
    if (vis[u] == t) return 0;
    vis[u] = t;
    for (int v : g[u])
      if (vis[v] != t && mch[v] == -1) return mch[v] = u, vis[v] = t, 1;
    for (int v : g[u]) {
      if (vis[v] != t) {
        if (vis[v] = t; self(self, mch[v], t)) return mch[v] = u, 1;
      }
    }
    return 0;
  };
  int ret = 0;
  vector < int > ord(l);
  iota(ord.begin(), ord.end(), 0);
  shuffle(ord.begin(), ord.end(), mt19937 (random_device{}()));
  for (int i : ord) ret += dfs(dfs, i, i);
  cout << ret << '\n';
  for (int i = 0; i < r; i++) {
    if (~mch[i]) cout << mch[i] << ' ' << i << '\n';
  }
  return 0;
}