#include <iostream>
#include <fstream>
#include <bitset>
#include <vector>

using namespace std;
typedef vector<int>::iterator iter;

#define MAXN 10005

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

int n, m;
vector<int> G[MAXN];
bitset<MAXN> viz;
int r[MAXN], l[MAXN];

bool match(int nd)
{
    if (viz[nd] == true) {
        return false;
    }
    viz[nd] = true;

    for (iter it = G[nd].begin(); it != G[nd].end(); it++) {
        if (r[*it] == 0) {
            l[nd] = *it;
            r[*it] = nd;
            return true;
        }
    }

    for (iter it = G[nd].begin(); it != G[nd].end(); it++) {
        if (match(r[*it]) == true) {
            l[nd] = *it;
            r[*it] = nd;
            return true;
        }
    }

    return false;
}

int main()
{
    int e;
    f >> n >> m >> e;
    for (int i = 1; i <= e; i++) {
        int x, y;
        f >> x >> y;
        G[x].push_back(y);
    }

    bool ok = true;
    while (ok) {
        ok = false;

        viz.reset();
        for (int i = 1; i <= n; i++) {
            if (l[i] == 0) {
                ok |= match(i);
            }
        }
    }

    int sol = 0;
    for (int i = 1; i <= n; i++) {
        if (l[i] != 0) {
            sol++;
        }
    }

    g << sol << '\n';
    for (int i = 1; i <= n; i++) {
        if (l[i] != 0) {
            g << i << ' ' << l[i] << '\n';
        }
    }

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