#include <bits/stdc++.h>

using namespace std;

const int kNmax = 1e4+4;

int l[kNmax], r[kNmax];
bool use[kNmax];
vector<int> g[kNmax];

bool pair_up(int which) {
  if (use[which]) return false;
  use[which] = true;
  
  for (int y : g[which]) {
    if (!r[y]) {
      l[which] = y;
      r[y] = which;
      return true;
    }
  }
  
  for (int y : g[which]) {
    if (pair_up(r[y])) {
      l[which] = y;
      r[y] = which;
      return true;
    }
  }
  
  return false;
}

int main() {
  #ifdef INFOARENA
  freopen("cuplaj.in", "r", stdin);
  freopen("cuplaj.out", "w", stdout);
  #endif
  
  int n, m, e;
  cin >> n >> m >> e;
  for (int u, v, i = 1; i <= e; i++) {
    cin >> u >> v;
    g[u].push_back(v);
  }
  
  for (bool ok = true; ok; ) {
    ok = false;
    memset(use, false, sizeof use);
    for (int i = 1; i <= n; i++)
      if (!l[i])
        ok |= pair_up(i);
  }
  
  vector<pair<int, int> > matching;
  for (int i = 1; i <= n; i++) {
    if (!l[i]) continue;
    matching.emplace_back(i, l[i]);
  }
  
  cout << matching.size() << '\n';
  for (const auto& pii : matching) {
    cout << pii.first << ' ' << pii.second << '\n';
  }
  
  return 0;
}