#include <vector>
#include <fstream>
#include <cstring>

using namespace std;

ifstream cin("cuplaj.in");
ofstream cout("cuplaj.out");

const int N = 100100;

vector<int> v[N];
int n, m, p, r[N], l[N], x, y, nrc, viz[N];

int cuplaj(int x) {
  if (viz[x]) {
    return 0;
  }
  viz[x] = 1;
  for (auto &it: v[x]) {
    if (!r[it]) {
      l[x] = it;
      r[it] = x;
      return 1;
    }
  }

  for (auto &it: v[x]) {
    if (cuplaj(r[it])) {
      l[x] = it;
      r[it] = x;
      return 1;
    }
  }

  return 0;
}

int main () {
  cin >> n >> m >> p;
  for (int i = 1; i <= p; ++i) {
    cin >> x >> y;
    v[x].push_back(y);
  }

  int ok = 1;
  while (ok) {
    ok = 0;
    memset(viz, 0, sizeof(viz));
    for (int i = 1; i <= n; ++i) {
      if (!l[i] && cuplaj(i)) {
        nrc++;
        ok = 1;
      }
    }
  }

  cout << nrc << "\n";
  
  for (int i = 1; i <= n; ++i) {
    if (l[i]) {
      cout << i << " " << l[i] << "\n";
    }
  }
}