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

int l[10005], r[10005];
int s[10005];
typedef struct nod {
        int vf;
        nod* next;
} NOD, *PNOD;
PNOD v[10001];

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 ( k = 1; k <= m; k++ )
        scanf("%d %d", &i, &j),
        Add(i, j);
    k = 0;
    for (int change = 1; change; )
    {
        change = 0;
        k++;
        for ( i = 1; i <= e; i++ )
            if ( r[i] == 0 ) 
                change |= DFM(i);
    }
    for (i = 1; i <= e; i++ ) rez += (r[i] > 0);
    printf("%d\n", rez);
    for ( i = 1; i <= e; i++ )
        if ( r[i] != 0 )
           printf("%d %d\n", i, r[i]);
    return 0;
}

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

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