#include<fstream>
#include<vector>
#include<bitset>
using namespace std;
#define NMAX 10005
ifstream fin("cuplaj.in");
ofstream fout("cuplaj.out");
vector <int> v[NMAX];
bitset <NMAX> viz;
int n,m,k,x,y,nr,L[NMAX],R[NMAX];
bool ok;
bool cupleaza(int nod)
{
    vector <int>::iterator it;
    if (viz[nod]) return false;
    viz[nod]=1;
    for (it=v[nod].begin();it!=v[nod].end();++it)
        if (!R[*it])
        {
            L[nod]=*it, R[*it]=nod;
            return true;
        }
    for (it=v[nod].begin();it!=v[nod].end();++it)
        if (cupleaza(R[*it]))
        {
            L[nod]=*it, R[*it]=nod;
            return true;
        }
    return false;
}
int main()
{
    int i;
    fin>>n>>m>>k;
    for (i=0;i<k;++i)
    {
        fin>>x>>y;
        v[x].push_back(y);
    }
    for (ok=true;ok;)
    {
        ok=false;
        viz.reset();
        for (i=1;i<=n;++i)
            if (!L[i] && cupleaza(i))
                ok=true;
    }
    for (i=1;i<=n;++i)
        if (L[i]) ++nr;
    fout<<nr<<"\n";
    for (i=1;i<=n;++i)
        if (L[i])
            fout<<i<<" "<<L[i]<<"\n";
    return 0;
}