#include <stdio.h>
#define N 10000

int h[20001];
int s[20001];
typedef struct nod {
        int vf;
        nod* next;
} NOD, *PNOD;

PNOD l[20001];
int e, g, m;
int i, j, k, rez;
void Add(int i, int j);
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++ ) h[i] = -1;
    for ( i = 1; i <= g; i++ ) h[i+N] = -1;
    
    for ( k = 1; k <= m; k++ )
        scanf("%d %d", &i, &j),
        Add(i, j+N);
    k = 0;
    for ( i = 1; i <= e; i++ )
    {
        if ( h[i] == -1 ) 
           k++,
           rez += DFM(i);
    }
    printf("%d\n", rez);
    for ( i = 1; i <= e; i++ )
        if ( h[i] != -1 )
           printf("%d %d\n", i, h[i]-N);
    return 0;
}

void Add(int i, int j)
{
     PNOD q = new NOD;
     q->vf = j;
     q->next = l[i];
     l[i] = q;
}

int DFM(int nod)
{
    if ( s[nod] == k ) return 0;
    s[nod] = k;
    for ( PNOD q = l[nod]; q; q = q->next )
        if ( h[q->vf] == -1 )
        {
             h[q->vf] = nod;
             h[nod] = q->vf;
             return 1;
        }
    for ( PNOD q = l[nod]; q; q = q->next )
        if ( s[q->vf] != k )
        {
             s[q->vf] = k;
             if ( DFM(h[q->vf]) )
             {
                  h[q->vf] = nod;
                  h[nod] = q->vf;
                  return 1;
             }
        }
    return 0;
}