#include <bits/stdc++.h>
using namespace std;
using i64 = long long;
constexpr int N = 1e5 + 5;
bitset < N > to[N], vis, ave;
int l, r, m, mch[N];
int dfs(int u) {
  if (vis[u]) return 0;
  vis[u] = 1;
  while (1) {
    int v = (to[u] & ave)._Find_first();
    if (v == N) return 0;
    ave[v] = 0;
    if (!mch[v] || dfs(mch[v])) return mch[v] = u, 1;
  }
  return 0;
}

int main() {
  cin.tie(nullptr)->sync_with_stdio(false);
  cin >> l >> r >> m;
  for (int i = 1, u, v; i <= m; i++) {
    cin >> u >> v; u++, v++;
    to[u][v] = 1;
  }
  int ret = 0;
  for (int i = 1; i <= l; i++) ave.set(), vis.reset(), ret += dfs(i);
  cout << ret << '\n';
  for (int i = 1; i <= l; i++) {
    if (mch[i]) cout << i - 1 << ' ' << mch[i] - 1 << '\n';
  }
  return 0;
}