#include <bits/stdc++.h>

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

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