#include <stdio.h>
#include <vector>
#include <algorithm>
using namespace std;

int l[10001], r[10001];
int s[10001];
vector<int> v[10001];
vector<int>::iterator it;

int e, g, m;
int i, j, k, rez;
int DFM(int nod);

int main()
{
    freopen("cuplaj.in", "r", stdin);
    freopen("cuplaj.out", "w", stdout);
    scanf("%d %d %d", &e, &g, &m);
    for ( i = 1; i <= e; i++ ) r[i] = -1;
    for ( i = 1; i <= g; i++ ) l[i] = -1;
    
    for ( k = 1; k <= m; k++ )
        scanf("%d %d", &i, &j),
        v[i].push_back(j);
    k = 0;
    for ( i = 1; i <= e; i++ )
    {
        if ( r[i] == -1 ) 
           k++,
           rez += DFM(i);
    }
    printf("%d\n", rez);
    for ( i = 1; i <= e; i++ )
        if ( r[i] != -1 )
           printf("%d %d\n", i, r[i]);
    return 0;
}

int DFM(int nod)
{
    if ( s[nod] == k ) return 0;
    s[nod] = k;
    for ( it = v[nod].begin(); it != v[nod].end(); it++ )
        if ( l[*it] == -1 )
        {
             l[*it] = nod;
             r[nod] = *it;
             return 1;
        }
    for ( it = v[nod].begin(); it != v[nod].end(); it++ )
        if ( DFM(l[*it]) )
        {
             l[*it] = nod;
             r[nod] = *it;
             return 1;
        }
    return 0;
}