// Algoritmului lui Hopcroft Karp
// Complexitate O(sqrt(V)*E)
#include <fstream>
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

ifstream fin("cuplaj.in");
ofstream fout("cuplaj.out");

using VI = vector<int>;
vector<VI> G;
VI l, r, u;
int N, M, E;

void ReadGraph();
void HopcroftKarp();
bool PairUp( int x );
void Write();

int main()
{
    ReadGraph();

  /*  for ( int i = 1; i <= N; ++i )
    {
        cout << i << ": ";
        for ( const int& x : G[i] )
            cout << x << ' ';
        cout << '\n';
    }       */

    HopcroftKarp();
    Write();

    fin.close();
    fout.close();
    return 0;
}

void ReadGraph()
{
    int x, y;

    fin >> N >> M >> E;
    G = vector<VI>(N + 1);
    u = l = VI(N + 1);
    r = VI(M + 1);
    while ( E-- )
    {
        fin >> x >> y;
        G[x].push_back(y);
    }
}

void HopcroftKarp()
{
    bool gt = false;

    while ( !gt )
    {
        gt = true;
        u = VI(N + 1, 0);

        for ( int i = 1; i <= N; ++i )
            if ( !l[i] )
                if ( PairUp(i) )
                {
                    gt = false;
                }
    }
}

bool PairUp( int x )
{
    if ( u[x] ) return false;
    u[x] = 1;

    for ( const auto& v : G[x] )
        if ( !r[v] )
        {
            l[x] = v;
            r[v] = x;
            return true;
        }

    for ( const auto& v : G[x] )
        if ( PairUp(r[v]) )
        {
            l[x] = v;
            r[v] = x;
            return true;
        }

    return false;
}

void Write()
{
    int cuplaj{0};

    for ( int i = 1; i <= N; ++i )
        if ( l[i] )
            ++cuplaj;

    fout << cuplaj << '\n';
    for ( int i = 1; i <= N; ++i )
        if ( l[i] )
            fout << i << ' ' << l[i] << '\n';
}