#include <fstream>
#include <vector>
#include <bitset>
using namespace std;

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

const int NMAX = 1e4 + 1;

vector <int> g[NMAX];
vector <int> l;
vector <int> r;
bitset <NMAX> used;
bool pairUp(int node)
{
    if (used[node])
        return 0;

    used[node] = 1;

    for (auto i : g[node])
        if (!l[i])
        {
            l[i] = node;
            r[node] = i;
            return 1;
        }
    for (auto i : g[node])
        if (pairUp(l[i]))
        {
            l[i] = node;
            r[node] = i;
            return 1;
        }
    return 0;
}

int x, y, n, m, e;

int main()
{
    fin >> n >> m >> e;

    for (int i = 1; i <= e; ++i)
    {
        fin >> x >> y;
        g[x].push_back(y);
    }

    r.resize(n + 1);
    l.resize(m + 1);

    int cnt = 0;

    bool ok = true;
    while (ok)
    {
        ok = false;
        used.reset();
        for (int i = 1; i <= n; ++i)
            if (!r[i] && pairUp(i))
            {
                ok = true;
                ++cnt;
            }
    }

    fout << cnt << '\n';

    for (int i = 1; i <= n; ++i)
        if (r[i])
            fout << i << " " << r[i] << '\n';

    return 0;
}