#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define MAXN  10005

int *G[MAXN];

int st[MAXN], dr[MAXN], u[MAXN];


int cupleaza(const int x)
{ int i;
    if (u[x])  return 0;
    u[x] = 1;
    for (i=1;i<=G[x][0];i++) 
     if (!dr[G[x][i]])
      {
	st[x] = G[x][i];
	dr[G[x][i]] = x;
	return 1;
      }
    for (i=1;i<=G[x][0];i++)
     if (cupleaza(dr[G[x][i]]))
      {
	st[x] =G[x][i];
	dr[G[x][i]] =x;
	return 1;
      }
    return 0;
}

int main(void)
{
    freopen("cuplaj.in", "r", stdin);
    freopen("cuplaj.out", "w", stdout);

    int n, m, e,i;
    scanf("%d %d %d", &n, &m, &e);

    for (i=1;i<=n;i++)
     {
       G[i]=(int*) realloc(G[i],sizeof(int));
       G[i][0]=0;
     }
    while (e--)
    {
        int x, y;
        scanf("%d %d", &x, &y);
        G[x][0]++;
	G[x]=(int*) realloc(G[x],(G[x][0]+1)*sizeof(int));
	G[x][G[x][0]]=y;
    }
    int change=1;
    while (change)
    {
        change = 0;
        memset(u, 0, sizeof(u));
	for (i=1;i<=n;i++)
         if (!st[i])
            change |= cupleaza(i);
    }

    int cuplaj = 0;
    for (i=1; i<=n;i++)  
     cuplaj += (st[i] > 0);
    printf("%d\n", cuplaj);
    for (i=1; i<=n;i++) 
     if (st[i] > 0)
       printf("%d %d\n", i, st[i]);

    return 0;
}