#include <fstream>
#include <list>
#include <string.h>
using namespace std;
ifstream f1("cuplaj.in");
ofstream f2("cuplaj.out");
#define MX 20*1001
#define NIL 0
#define INF 0x0fffffff
#define FORU(it,G) for(list<int>::iterator it=G.begin(); it != G.end(); it++)

int n,m, e, nr_cuplaje;

list<int> Graf[MX];

int Pair[MX], dist[MX];

bool BFS()
{
    int u;
    list<int> Q;

    for (u=1; u<=n; u++)
        if ( Pair[u] == NIL )
        {
            Q.push_back(u);
            dist[u]= 0;
        }
        else
            dist[u]= INF;

    dist[NIL]= INF;

    while ( !Q.empty() )
    {
        u= *Q.begin();
        Q.pop_front();

        if ( dist[u] < dist[NIL] )
            FORU(v,Graf[u])
                if ( dist[ Pair[*v] ] == INF )
                {
                    dist[ Pair[*v] ]= dist[u]+1;
                    Q.push_back( Pair[*v] );
                }
    }

    return dist[NIL] != INF;
}

bool DFS(int nod)
{
    if ( nod != NIL)
    {
        FORU(v,Graf[nod])
            if ( dist[ Pair[*v] ] == dist[nod]+1 )
                if ( DFS( Pair[*v] ) )
                {
                    Pair[*v]= nod;
                    Pair[nod]= *v;
                    return true;
                }
        return false;
    }

    return true;
}

void Hopfkropf_Karp()
{
    int u;

    while ( BFS() )
        for (u=1; u<=n; u++)
            if ( Pair[u] == NIL && DFS(u) ) // u can be paired
                nr_cuplaje++;
}

int main()
{
    int i, x, y;

    f1>>n>>m>>e;

    for (i=1; i<=e; i++)
    {
        f1>>x>>y;
        Graf[x].push_back( y + n );         // inlocuiesc y cu y+n
        Graf[ y + n ].push_back(x);
    }

    Hopfkropf_Karp();

    f2<<nr_cuplaje<<"\n";

    for (i=1; i<=n; i++)
        if ( Pair[i] != NIL )
            f2<<i<<" "<<Pair[i] - n<<"\n";  // pun y din graful initial

    f2.close();
    return 0;
}