#include <fstream>
#include <vector>

using namespace std;

typedef vector<vector<int>> Muchii;

bool Cupleaza(int nod, const Muchii &m, vector<int> &p1, vector<int> &p2, vector<bool> &viz)
{
    if (viz[nod]) return false;
    viz[nod] = true;

    for (int vecin : m[nod]) {
        if (p2[vecin] == 0 ||
            Cupleaza(p2[vecin], m, p1, p2, viz)) {

                p1[nod] = vecin;
                p2[vecin] = nod;
                return true;
        }
    }
    return false;
}

vector<pair<int, int>> AflaCuplaj(const Muchii &muc, int n, int m)
{
    vector<int> pereche1(n + 1, 0);
    vector<int> pereche2(m + 1, 0);

    bool modificari;
    do{
        modificari = false;
        vector<bool> vizitat(n + 1, false);

        for (int i = 1; i <= n; ++i) {
            if (pereche1[i] == 0 && Cupleaza(i, muc, pereche1, pereche2, vizitat))
                modificari = true;
        }
    } while (modificari);

    vector<pair<int, int>> cuplaj;
    for (unsigned i = 1; i < pereche1.size(); ++i)
        if (pereche1[i] != 0)
            cuplaj.push_back({i, pereche1[i]});
    return cuplaj;
}

int main()
{
    ifstream fin("cuplaj.in");
    ofstream fout("cuplaj.out");

    int n, m, k;
    fin >> n >> m >> k;

    Muchii vecini(n + 1);
    while (k--) {
        int x, y;
        fin >> x >> y;
        vecini[x].push_back(y);
    }

    auto cuplaj = AflaCuplaj(vecini, n, m);
    fout << cuplaj.size() << "\n";
    for (auto &p : cuplaj)
        fout << p.first << " " << p.second << "\n";

    return 0;
}