#include <algorithm>
#include <iostream>
#include <fstream>
#include <vector>
#include <queue>

using namespace std;
ifstream f("cuplaj.in");
ofstream g("cuplaj.out");
int n, m, e;
vector<int> la[100001];
queue<int> q;
vector<int> st, dr, dist;



bool BFS()
{
    for (int i = 1; i <= n; i++)
        if (!dr[i])//daca nodurile din stanga au un corespondent in dreapta
        {
            q.push(i);
            dist[i] = 0;
        }
        else
            dist[i] = 999999;
    dist[0] = 999999;
    //q = nodurile din parte stanga
    while (!q.empty())
    {
        int nod = q.front();
        q.pop();
        if (dist[nod] < dist[0])
        {
            for (int i=0;i<la[nod].size();i++)
            {
                int urm=la[nod][i];
                if (dist[st[urm]] == 999999)
                {
                    dist[st[urm]] = 1 + dist[nod];
                    q.push(st[urm]);
                }
            }
        }
    }
    return dist[0] != 999999;
}
bool DFS(int nod)
{
    if (nod != 0)
    {
        for (int i=0;i<la[nod].size();i++){
            int urm=la[nod][i];
            if (1 + dist[nod] == dist[st[urm]] && DFS(st[urm]))
            {

                st[urm] = nod;
                dr[nod] = urm;
                return true;
            }}
        dist[nod] = 999999;
        return false;
    }
    return true;
}
int cuplajMax()
{
    int rez = 0;
    while (BFS())
    {
        for (int i = 1; i <= n; i++)
            if (!dr[i] && DFS(i))
                rez++;
    }
    return rez;
}
int main()
{
    f >> n >> m >> e;
    st.resize(n + 1, 0);
    dr.resize(n + 1, 0);
    dist.resize(n + 1, 0);
    for (int i = 1; i <= e; i++)
    {
        int x, y;
        f >> x >> y;
        la[x].push_back(y);
    }
    g << cuplajMax() << '\n';
    for (int i = 1; i <= m; i++)
        if (st[i])
            g << st[i] << ' ' << i << '\n';
    return 0;
}