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

using namespace std;

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

int n, m, e, ans;
int l[10100], r[20100];
bool fr[10100];
vector<vector<int>> adj;

bool chain(int node)
{
    if(fr[node])
        return 0;

    fr[node] = 1;

    for(auto it: adj[node])
    {
        if(r[it] == 0)
        {
            l[node] = it;
            r[it] = node;
            //cout << node << ' ' << it << '\n';
            return 1;
        }
    }

    for(auto it: adj[node])
    {
        if(chain(r[it]))
        {
            l[node] = it;
            r[it] = node;
            //cout << node << ' ' << it << '\n';
            return 1;
        }
    }

    return 0;
}

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(n + y);
    }

    bool ok = 1;

    while(ok)
    {
        //cout << "ITERATION:\n";

        memset(fr, 0, sizeof fr);
        ok = 0;

        for(int i = 1; i <= n; i++)
        {
            if(!l[i])
            {
                //cout << "INDEX: " << i << '\n';
                ok |= chain(i);
            }
        }
    }

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

    out << ans << '\n';

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

    return 0;
}