#include <bitset>
#include <vector>
#include <fstream>
#include <cstdlib>

using namespace std;

const int N_MAX=10011;

int L[N_MAX], R[N_MAX];

bitset<N_MAX> was;
vector<int> G[N_MAX];

inline bool PairUp(int x)
{
    if(true == was.test(x))
        return false;
    was.set(x);
    vector<int>::const_iterator it=G[x].begin(), iend=G[x].end();

    for(; it < iend; ++it)
        if(!R[*it] || PairUp(R[*it]))
        {
            L[x]=*it;
            R[*it]=x;
            return true;
        }
    return false;
}
int main()
{
    bool ok;
    int N, M, E, x, y, i, countMatch=0;
    ifstream in("cuplaj.in");
    ofstream out("cuplaj.out");

    for(in>>N>>M>>E; E; --E)
    {
        in>>x>>y;
        G[x].push_back(y);
    }
    do {
            ok=false;
            for(i=1; i <= N; ++i)
                if(!L[i] && PairUp(i))
                    ok=true, ++countMatch;
            was&=0;
       }while(ok);
    out<<countMatch<<'\n';
    for(i=1; i <= N; ++i)
        if(L[i])
            out<<i<<' '<<L[i]<<'\n';

    return EXIT_SUCCESS;
}