#include <iostream>
#include <fstream>
#include <vector>
#include <cstring>

using namespace std;

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

int n, m, e, sol;
int l[10100], r[10100];
bool use[10100];
vector<vector<int>> adj;

void connect(int a, int b)
{
    l[a] = b;
    r[b] = a;
}

bool chain(int node)
{
    if(use[node] == true)
        return false;

    use[node] = true;

    for(auto it : adj[node])
    {
        if(r[it] == 0)
        {
            connect(node, it);
            return true;
        }
    }

    for(auto it : adj[node])
    {
        if(chain(r[it]) == true)
        {
            connect(node, it);
            return true;
        }
    }

    return false;
}

int main()
{
    in >> n >> m >> e;

    adj.resize(n + 5);

    for(int i = 1; i <= e; i++)
    {
        int x,y;
        in >> x >> y;

        adj[x].push_back(y);
    }

    bool ok = true;

    while(ok)
    {
        ok = false;
        memset(use, false, sizeof use);

        for(int i = 1; i <= n; i++)
            if(l[i] == 0)
                ok = (ok || chain(i));
    }

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

    out << sol << '\n';

    for(int i = 1; i <= n; i++)
        if(l[i] != 0)
            out << i << ' ' << l[i] << '\n';

    return 0;
}