#include <fstream>
#include <vector>
using namespace std;

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

int l, r, m;

vector <int> v[10005];

int lleft[10005], rright[10005], aux[10005];

bool pairup(int x)
{
    if(aux[x] != 0)
        return false;

    aux[x] = 1;

    for(int i = 0; i < v[x].size(); i++)
        if(rright[v[x][i]] == 0)
    {
        lleft[x] = v[x][i];
        rright[v[x][i]] = i + 1;
        return true;
    }

    for(int i = 0; i < v[x].size(); i++)
        if(pairup(rright[v[x][i]]) != 0)
    {
        lleft[x] = v[x][i];
        rright[v[x][i]] = i + 1;
        return true;
    }

    return false;
}

int main()
{
    fin >> l >> r >> m;

    for(int i = 1; i <= m; i++)
    {
        int x, y;

        fin >> x >> y;

        v[x].push_back(y);
    }

    bool ok = true;

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

        fill(aux + 1, aux + 10001, 0);

        for(int i = 1; i <= l; i++)
            if(lleft[i] == 0)
                ok = pairup(i);
    }

    int card = 0;

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

    fout << card << '\n';

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

    return 0;
}