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

using namespace std;

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

const int SIZE = 10005;
const int INF = 0x3f3f3f3f;

int st, dr, ans;

vector <int> adj[SIZE];
vector <int> pair_st(SIZE, 0);
vector <int> pair_dr(SIZE, 0);
vector <int> dist(SIZE, 0);

void Read()
{
    int len;
    f >> st >> dr >> len;
    for (int i = 1; i <= len; i++)
    {
        int x, y;
        f >> x >> y;
        adj[x].push_back(y);
    }
}

bool BFS()
{
    queue <int> q;

    for (int i = 1; i <= st; i++)
    {
        if (pair_st[i] == 0)
        {
            dist[i] = 0;
            q.push(i);
        }
        else
        {
            dist[i] = INF;
        }
    }

    dist[0] = INF;
    while (q.empty() == false)
    {
        int node = q.front();
        q.pop();

        if (dist[node] < dist[0])
        {
            for (unsigned int i = 0; i < adj[node].size(); i++)
            {
                int neighbour = adj[node][i];

                if (dist[pair_dr[neighbour]] == INF)
                {
                    dist[pair_dr[neighbour]] = dist[node] + 1;
                    q.push(pair_dr[neighbour]);
                }
            }
        }
    }

    return (dist[0] != INF);
}

bool DFS(int node)
{
    if (node != 0)
    {
        for (unsigned int i = 0; i < adj[node].size(); i++)
        {
            int neighbour = adj[node][i];

            if (dist[pair_dr[neighbour]] == dist[node] + 1)
            {
                if (DFS(pair_dr[neighbour]) == true)
                {
                    pair_dr[neighbour] = node;
                    pair_st[node] = neighbour;

                    return true;
                }
            }
        }

        dist[node] = INF;
        return false;
    }

    return true;
}

void HopkroftKarp()
{
    while (BFS() == true)
    {
        for (int i = 1; i <= st; i++)
        {
            if (pair_st[i] == 0 && DFS(i) == true)
            {
                ans++;
            }
        }
    }
}

void Print()
{
    g << ans << "\n";
    for (int i = 1; i <= st; i++)
    {
        if (pair_st[i] != 0)
        {
            g << i << " " << pair_st[i] << "\n";
        }
    }
}

int main()
{
    Read();
    HopkroftKarp();
    Print();

    return 0;
}