#include <fstream>
#include <iostream>
#include <vector>
#define DIM 20100

using namespace std;

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

int N,M,nr,ok,B;

vector <int> L[DIM],r(DIM),l(DIM),v(DIM);

int cuplaj(int nod){
    v[nod]=1;
    for(int i=0;i<L[nod].size();i++)
        if(r[L[nod][i]]==0){
            l[nod]=L[nod][i];
            r[L[nod][i]]=nod;
            return 1;
        }

    for(int i=0;i<L[nod].size();i++)
        if(!v[r[L[nod][i]]] && cuplaj(r[L[nod][i]])){
            l[nod] = L[nod][i];
            r[L[nod][i]]=nod;
            return 1;
        }

    return 0;

}

int main(){
    fin >> N >> M >> B;

    while(B--){
        int x,y;
        fin >> x >> y;
        L[x].push_back(y+N);
    }

    M = max(N,M);

    do{
        ok=0;
        for(int i=1;i<=M;i++){
            v[i]=0;
        }
        for(int i=1;i<=N;i++){
            if(!l[i] && cuplaj(i)){
                nr++;
                ok=1;
            }
        }
    }while(ok);

    fout << nr << "\n";

    for(int i=1;i<=N;i++)
        if(l[i])
            fout << i << " " << l[i]-N << "\n";

    return 0;

}