#include <bits/stdc++.h>

using namespace std;
ifstream f("cuplaj.in");
ofstream g("cuplaj.out");
int l[10001], r[10001];
int n, m, p;
vector<int> graf[10001];
bool viz[10001];

void read()
{
  f>>n>>m>>p;
  int x, y;
  for(int i = 1;i <= p;++i)
    f>>x>>y, graf[x].push_back(y);
}

bool verify(int node)
{
  if(viz[node]) return false;
  viz[node] = true;

  for(auto it : graf[node])
    if(!r[it])
    {
      r[it] = node;
      l[node] = it;
      return true;
    }
  
  for(auto it : graf[node])
    if(verify(r[it]))
    {
      r[it] = node;
      l[node] = it;
      return true;
    }
  
  return false;
}

void solve()
{
  bool change = true;
  while(change)
  {
    change = false;
    memset(viz, false, sizeof(viz));

    for(int i = 1;i <= n;++i)
      if(!l[i])
        change |= verify(i);
  }
  int number = 0;
  for(int i = 1;i <= n;++i)
    number += (l[i] != 0);
  g<<number<<'\n';

  for(int i = 1;i <= n;++i)
    if(l[i])
      g<<i<<" "<<l[i]<<'\n';
}

int main()
{
  read();
  solve();
  return 0;
}