// Include
#include <fstream>
#include <cstring>
#include <vector>
using namespace std;
 
// Definitii
#define pb push_back
 
// Constante
const int sz = (int)1e5+8;
 
// Functii
int link(int node);
 
// Variabile
ifstream in("cuplaj.in");
ofstream out("cuplaj.out");
 
int leftNodes, rightNodes, edges;
int Left[sz], Right[sz];
bool Fixed[sz];
 
int answer;
vector<int> graph[sz];
 
// Main
int main()
{
    in >> leftNodes >> rightNodes >> edges;
    int rFrom, rTo;
    while(edges--)
    {
        in >> rFrom >> rTo;
        graph[rFrom].pb(rTo);
    }
     
    for(int i=1 ; i<=leftNodes ; ++i)
    {
        if(!link(i))
        {
            memset(Fixed, false, (leftNodes+1)*sizeof(bool));
            answer += link(i);
        }
        else
            ++answer;
    }
     
    out << answer << '\n';
    for(int i=1 ; i<=leftNodes ; ++i)
        if(Right[i])
            out << i << ' ' << Right[i] << '\n';
     
    in.close();
    out.close();
    return 0;
}
 
int link(int node)
{
    if(Fixed[node])
        return 0;
    Fixed[node] = true;
     
    vector<int>::iterator it, end=graph[node].end();
    for(it=graph[node].begin() ; it!=end ; ++it)
    {
        if(!Left[*it])
        {
            Left[*it] = node;
            Right[node] = *it;
            return 1;
        }
    }
     
    for(it=graph[node].begin() ; it!=end ; ++it)
    {
        if(link(Left[*it]))
        {
            Left[*it] = node;
            Right[node] = *it;
            return 1;
        }
    }
     
    return 0;
}