#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
 
using namespace std;
 
vector<int>* vec;
int *st, *dr, *viz;
int s, d, e, n;
 
void citeste ( const char file[] ) {
    ifstream in;
    in.open ( file );
    in >> s >> d >> e;
    vec = new vector<int> [ s+d+1 ];
    int i, a, b;
    for ( i = 1; i <= e; i++ ) {
        in >> a >> b;
        vec[a].push_back ( b );
    }
    in.close();
}
 
int cupleaza ( int x ) {
    if ( viz[x] == 1 )
        return 0;
    viz[x] = 1;
    int i;
    for ( i = 0; i < vec[x].size(); i++ ) //cauta un nod din stanga adiacent cu x care nu este cuplat
        if ( dr[vec[x][i]] == 0 ) {
            st[x] = vec[x][i];
            dr[vec[x][i]] = x;
            return 1;
        }
    for ( i = 0; i < vec[x].size(); i++ ) // daca nu se reuseste pasul anterior, se cupleaza x cu nod y deja ales
										//si se cauta un alt nod adiacent pentru nodul de care era legat y.....  
        if ( cupleaza ( dr[vec[x][i]] ) == 1 ) {
            st[x] = vec[x][i];
            dr[vec[x][i]] = x;
            return 1;
        }
    return 0;
}
 
void cuplajMax( const char file[] ) {
    int ok = 1, x = 0, i;
    while ( ok == 1 ) { //cat timpm se face o modificare
        ok = 0;  
        for ( i = 1; i <= s; i++ ) 
            viz[i] = 0;
        for ( i = 1; i <= s; i++ )
            if ( st[i] == 0 ) //daca este un nod necuplat
                if ( cupleaza (i) == 1 )  //daca rezultatul este 1 adunci s-a reusit cuplarea lui
                    ok = 1;
    }
    ofstream out;
    out.open ( file );
    for ( i = 1; i <= s; i++ )
        if ( st[i] > 0 )
            x++;
	
    out << x << '\n';
    for ( i = 1; i <= s; i++ )
        if ( st[i] != 0 )
            out << i << ' ' << st[i] << '\n';
    out.close();
}
 
int main() {
    citeste( "cuplaj.in" );
	
    st = new int [s+1];
    dr = new int [d+1];
    viz = new int [s+1];
    int i;
    for ( i = 1; i <= s; i++ ) {
        st[i] = 0;
        viz[i] = 0;
    }
    for ( i = 1; i <= d; i++ )
        dr[i] = 0;
    cuplajMax( "cuplaj.out" );
    return 0;
}