#include <bits/stdc++.h>
#define dbg(x) cerr << (#x) << ": " << x << "\n\n";
using namespace std;
const int NMAX = 1e4 + 5, MOD = 1e9 + 7;

bool viz[NMAX], deja[NMAX];
int n, m, e, mt[NMAX], sz;
vector<int> v[NMAX];

bool kuhn (int x)
{
  viz[x] = true;
  for (auto u : v[x])
    if (!viz[mt[u]] && (!mt[u] || kuhn(mt[u])))
    {
      mt[u] = x;
      deja[x] = true;
      return true;
    }
  return false;
}

signed main ()
{
#ifndef MOOLAMP
  freopen("cuplaj.in", "r", stdin);
  freopen("cuplaj.out", "w", stdout);
#endif
  cin.tie(nullptr)->sync_with_stdio(false);
  cin >> n >> m >> e;
  while (e--)
  {
    int x, y; cin >> x >> y;
    v[x].push_back(y);
  }
  for (int i = 1; i <= n; i++)
    for (auto u : v[i])
      if (!mt[u])
      {
        sz++;
        mt[u] = i;
        deja[i] = true;
        break;
      }
  for (int i = 1; i <= n; i++)
    if (!deja[i])
    {
      fill(viz + 1, viz + n + 1, false);
      sz += kuhn(i);
    }
  cout << sz << '\n';
  for (int i = 1; i <= m; i++)
    if (mt[i])
      cout << mt[i] << ' ' << i << '\n';
}