#include <fstream>
#include <vector>
#include <cstring>
#define dim 200005
using namespace std;
ifstream fin("cuplaj.in");
ofstream fout("cuplaj.out");
int n,i,j,Left[dim],Right[dim],m,viz[dim],a,b,ok,e,sol;
vector<int> v[dim];
int cuplaj(int nod){
    viz[nod]=1;
    for(int i=0; i<v[nod].size();i++){
        int vecin = v[nod][i];
        if(Right[vecin]==0){
            Left[nod]=vecin;
            Right[nod]=nod;
            return 1;
        }
    }
    for(int i=0; i<v[nod].size();i++){
        int vecin = v[nod][i];
        if(viz[Right[vecin]]==0 && cuplaj(Right[vecin])){
            Left[nod]=vecin;
            Right[vecin]=nod;
            return 1;
        }
    }

    return 0;
}
int main(){
    fin>>n>>m>>e;
    for(i=1;i<=e;i++){
        fin>>a>>b;
        v[a].push_back(b);
    }
    ok=1;

    while(ok==1){
        ok=0;
        memset(viz,0,sizeof(viz));
        for(i=1;i<=n;i++){
            if(Left[i]==0 && cuplaj(i)){
                ok=1;
                sol++;
            }
        }
    }
    fout<<sol<<"\n";
    for(i=1;i<=n;i++){
        if(Left[i]!=0){
            fout<<i<<" "<<Left[i]<<"\n";
        }
    }


    return 0;
}