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

const int nmax = 1e5;

int n, m, e;
vector<int> adj[nmax];
vector<int> dist, upair, vpair;

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

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

  upair.resize(n, m);;
  vpair.resize(m, n);
  dist.resize(n + 1);

  while (bfs()) {
    for (int u = 0; u < n; u++) {
      if (upair[u] == m) {
        dfs(u);
      }
    }
  }

  vector<pair<int, int>> v;

  for (int i = 0; i < n; i++) {
    if (upair[i] == m) continue;
    v.push_back({i, upair[i]});
  }

  cout << v.size() << endl;
  for (auto [u, k] : v) {
    cout << u + 1 << ' ' << k + 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();
}