#include <cstdio>
#include <vector>
#include <bitset>
using namespace std;

#define Nmax 10002

FILE *f = fopen ( "cuplaj.in", "r" );
FILE *g = fopen ( "cuplaj.out", "w" );

vector < int > G[Nmax];
bitset < Nmax > used;
int stanga[Nmax], dreapta[Nmax];

int PairUp ( int nod ){

    if ( used[nod] )
        return 0;

    vector < int > :: iterator it;

    used[nod] = 1;

    for ( it = G[nod].begin(); it < G[nod].end(); ++it ){
        if ( !dreapta[*it] ){
            stanga[nod] = *it;
            dreapta[*it] = nod;
            return 1;
        }
    }

    for ( it = G[nod].begin(); it < G[nod].end(); ++it ){
        if ( PairUp ( dreapta[*it] ) ){
            stanga[nod] = *it;
            dreapta[*it] = nod;
            return 1;
        }
    }
    return 0;
}

int main(){

    int N1, N2, M, x, y;

    fscanf ( f, "%d%d%d", &N1, &N2, &M );

    for ( int i = 1; i <= M; ++i ){
        fscanf ( f, "%d%d", &x, &y );
        G[x].push_back ( y );
    }

    int schimb = 1;

    while ( schimb ){
        schimb = 0;
        used.reset();

        for ( int i = 1; i <= N1; ++i ){
            if ( !stanga[i] )
                schimb += PairUp( i );
        }
    }

    int matches = 0;

    for ( int i = 1; i <= N1; ++i )
        if ( stanga[i] )
            matches++;

    fprintf ( g, "%d\n", matches );

    for ( int i = 1; i <= N1; ++i )
        if ( stanga[i] )
            fprintf ( g, "%d %d\n", i, stanga[i] );

    return 0;
}