#include <bits/stdc++.h>

using namespace std;
#ifdef INFOARENA
ifstream fin("cuplaj.in");
ofstream fout("cuplaj.out");
#else
ifstream fin("ciorna.in");
ofstream fout("ciorna.out");
#endif // INFOARENA
class Matcher {
    int n, m;
    vector <int> l, r;
    vector <vector <int>> g;
    vector <bool> up;
    bool pairup(int u) {
        if(up[u]) return false;
        up[u] = true;
        for(int v : g[u]) if(!l[v])
            return r[l[v] = u] = v;
        for(int v : g[u]) if(pairup(l[v]))
            return r[l[v] = u] = v;
        return false;
    }
public:
    Matcher (int _n, int _m) : n(_n), m(_m), l(_m + 1, 0), r(_n + 1, 0), g(_n + 1), up(_n + 1) {}
    void add_edge(int u, int v) {
        g[u].push_back(v);
    }
    vector <pair <int, int>> match() {
        for(bool ok = true; ok;) {
            ok = false; fill(up.begin(), up.end(), false);
            for(int u = 1; u <= n; u++) if(!r[u])
                ok |= pairup(u);
        }
        vector <pair <int, int>> sol;
        for(int u = 1; u <= n; u++)
            if(l[r[u]] == u)
                sol.emplace_back(u, r[u]);
        return sol;
    }
};

int main()
{
    int n, m, e, u, v;
    fin >> n >> m >> e;
    Matcher M(n, m);
    for(int i = 1; i <= e; i++)
        fin >> u >> v,
        M.add_edge(u, v);
    vector <pair <int, int>> sol = M.match();
    fout << sol.size() << "\n";
    for(auto p : sol)
        fout << p.first << " " << p.second << "\n";
    return 0;
}