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

class Cuplaj {

  const vector<vector<int>> adj {};
  const int n = 0, m = 0;
  vector<int> lpair;
  vector<int> rpair;
  vector<int> dist;
  int match = 0;

  bool bfs() {
    queue<int> q;
    dist[n] = INT_MAX;
    for (int u = 0; u < n; u++) {
      if (lpair[u] != m) dist[u] = INT_MAX;
      else dist[u] = 0, q.push(u);
    }
    while (!q.empty()) {
      int u = q.front(); q.pop();
      if (dist[u] < dist[n]) {
        for (int v : adj[u]) {
          if (dist[rpair[v]] == INT_MAX) {
            dist[rpair[v]] = dist[u] + 1;
            q.push(rpair[v]);
          }
        }
      }
    }
    return dist[n] != INT_MAX;
  }

  bool dfs(int u) {
    if (u == n) return true;
    for (int v : adj[u]) {
      if (dist[rpair[v]] == dist[u] + 1) {
        if (dfs(rpair[v])) {
          lpair[u] = v;
          rpair[v] = u;
          return true;
        }
      }
    }
    dist[u] = INT_MAX;
    return false;
  }

  public:

  int matchingCount() {
    return match;
  }

  vector<pair<int, int>> matching() {
    vector<pair<int, int>> result;
    result.reserve(match);
    for (int u = 0; u < n; u++) {
      if (lpair[u] != m) {
        result.push_back({u, lpair[u]});
      }
    }
    return result;
  }

  Cuplaj(vector<vector<int>> adjacencyGraph, int leftNodes, int rightNodes) : adj(adjacencyGraph), n(leftNodes), m(rightNodes) {
    lpair.resize(n, m);
    rpair.resize(m, n);
    dist.resize(n + 1);
    while (bfs()) {
      for (int u = 0; u < n; u++) {
        if (lpair[u] == m) {
          if (dfs(u)) {
            match++;
          }
        }
      }
    }
  }

  Cuplaj() {}

};

void solve() {
  
  int n, m, e;
  cin >> n >> m >> e;
  vector<vector<int>> adj(n);

  for (int i = 0; i < e; i++) {
    int u, v;
    cin >> u >> v;
    adj[u - 1].push_back(v - 1);
  }

  vector<pair<int, int>> result = Cuplaj(adj, n, m).matching();

  cout << result.size() << '\n';
  for (const auto& [l, r] : result) {
    cout << (l + 1) << ' ' << (r + 1) << '\n';
  }

}

int main() {

  #ifdef LOCAL
  freopen("file.in", "r", stdin);
  #else
  freopen("cuplaj.in", "r", stdin);
  freopen("cuplaj.out", "w", stdout);
  #endif

  ios_base::sync_with_stdio(false), cin.tie(NULL);

  solve();
}