#include <fstream>
#include <vector>

const int NMAX = 10005;

using namespace std;

ifstream f("cuplaj.in");
ofstream g("cuplaj.out");

int N,M,E,x,y,L[NMAX],R[NMAX];
int maxitaxi,contor;
vector <int> v[NMAX];
bool change;
bool viz[NMAX];

bool cupleaza(int nod)
{
    if (viz[nod] == true)
        return false;
    viz[nod] = true;

    for (int i = 0; i < v[nod].size(); ++i)
    {
        int vecin = v[nod][i];
        if (!R[vecin])
        {
            L[nod] = vecin;
            R[vecin] = nod;
            return true;
        }
    }

    for (int i = 0; i < v[nod].size(); ++i)
    {
        int vecin = v[nod][i];
        if (cupleaza(R[vecin]))
        {
            L[nod] = vecin;
            R[vecin] = nod;
            return true;
        }
    }

    return false;
}

int main()
{
    f >> N >> M >> E;
    maxitaxi = max(N,M);

    for (int i = 1; i <= E; ++i)
    {
        f >> x >> y;
        v[x].push_back(y);
    }

    change = true;

    while(change)
    {
        change = false;
        for (int i = 1; i <= maxitaxi; ++i)
        {
            viz[i] = false;
        }

        for (int i = 1; i <= N; ++i)
        {
            if(!L[i])
            {
                if(cupleaza(i))
                    change = true;
            }
        }
    }

    for (int i = 1; i <= N; ++i)
    {
        if (L[i])
            contor++;
    }

    g << contor << '\n';

    for (int i = 1; i <= N; ++i)
    {
        if (L[i])
        {
            g << i << " " << L[i] << '\n';
        }
    }

    f.close();
    g.close();
    return 0;
}