#include <cstdio>
#include <vector>
#include <cstring>

using namespace std;

#define NMAX 10001

int left[NMAX],right[NMAX];
int E,N,M,X,Y,w,i;
bool marked[NMAX];
vector < int > G[NMAX];

bool can(int node)
{
    if (marked[node]) return false;
    marked[node]=true;

    for (vector < int > :: iterator u=G[node].begin();u!=G[node].end();++u)
    if (!right[*u])
    {
        left[node]=*u;
        right[*u]=node;
        return true;
    }

    for (vector < int > :: iterator u=G[node].begin();u!=G[node].end();++u)
    if (can(right[*u]))
    {
        left[node]=*u;
        right[*u]=node;
        return true;
    }

    return false;
}

void Cuplaj()
{
    int i,flag=true;

    for (;flag;)
    {
        flag=false;
        memset(marked,false,sizeof(marked));
        for (i=1;i<=N;++i)
        if (!left[i]) flag|=can(i);
    }
}

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

for (scanf("%d%d%d",&N,&M,&E);E;--E)
{
    scanf("%d%d",&X,&Y);
    G[X].push_back(Y);
}

Cuplaj();

for (i=1;i<=N;++i) w+=(left[i]>0);

for (i=1,printf("%d\n",w);i<=N;++i)
if (left[i]) printf("%d %d\n",i,left[i]);

return 0;
}