#include <iostream>
#include <vector>
#include <fstream>
#define nmax 10001
using namespace std;
ifstream f("cuplaj.in");
ofstream g("cuplaj.out");
vector <int> G[nmax];
vector <bool> Use(nmax);
int L[nmax],R[nmax];
int cuplaj(int nod){
    if(Use[nod]){
        return 0;
    }
    Use[nod]=1;
    for(int i=0;i<G[nod].size();i++){
        int nodul=G[nod][i];
        if(!R[nodul]){
            R[nodul]=nod;
            L[nod]=nodul;
            return 1;
        }
    }
    for(int i=0;i<G[nod].size();i++){
        int nodul=G[nod][i];
        if(cuplaj(R[nodul])){
            R[nodul]=nod;
            L[nod]=nodul;
            return 1;
        }
    }
    return 0;
}
int main()
{
    int n,m,k;
    f>>n>>m>>k;
    for(int i=0;i<k;i++){
        int x,y;
        f>>x>>y;
        G[x].push_back(y);
    }
    int ok=0,nr=0;
    do{
        ok=0;
        Use=vector<bool> (nmax,false);
        for(int i=1;i<=n;i++){
            if(L[i]==0){
                if(cuplaj(i)){
                    ok=1;
                    nr++;
                }
            }
        }
    }while(ok);
    g<<nr<<"\n";
    for(int i=1;i<=n;i++){
        if(L[i]){
            g<<i<<" "<<L[i]<<"\n";
        }
    }
    return 0;
}