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

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

const int Nmax = 10005;
vector <int> G[Nmax];
int l, r, m, L[Nmax], R[Nmax], Use[Nmax], nr;

int pairup(int nod)
{
    if(Use[nod]) return 0;
    Use[nod] = 1;
    for(int i = 0; i < (int)G[nod].size(); i++)
    {
        int vecin = G[nod][i];
        if(!R[vecin])
        {
            R[vecin] = nod;
            L[nod] = vecin;
            return 1;
        }
    }
    for(int i = 0; i < (int)G[nod].size(); i++)
    {
        int vecin = G[nod][i];
        if(pairup(vecin))
        {
            R[vecin] = nod;
            L[nod] = vecin;
            return 1;
        }
    }
    return 0;
}

int main()
{
    int ok = 0;
    f>>l>>r>>m;
    while(m--)
    {
        int x,y;
        f>>x>>y;
        G[x].push_back(y);
    }
    do
    {
        ok = 0;
        for(int i = 1; i <= l; i++)
        {
            if(L[i] == 0)
            {
                if(pairup(i))
                {
                    ok = 1;
                }
            }
        }
        memset(Use, 0, sizeof(Use));
    }while(ok == 1);
    for(int i = 1; i <= l; i++)
    {
        if(L[i]>0) nr++;
    }
    g<<nr<<'\n';
    for(int i = 1; i <= l; i++)
    {
        if(L[i] > 0) g<<L[i]<<' '<<i<<'\n';
    }
    return 0;
}