# include <fstream>
# include <vector>
# include <cstring>
# define DIM 10010
using namespace std;
ifstream fin("cuplaj.in");
ofstream fout("cuplaj.out");
vector <int> Lista[DIM];
int Marcat[DIM],r[DIM],l[DIM],n,m,nr,x,y,ok,i;
int cuplaj(int nod){
    if(Marcat[nod])
        return 0;
    Marcat[nod]=1;
    for(int i=0;i<Lista[nod].size();i++){
        int vecin=Lista[nod][i];
        if(!r[vecin]){
            r[vecin]=nod;
            l[nod]=vecin;
            return 1;
        }
    }
    for(int i=0;i<Lista[nod].size();i++){
        int vecin=Lista[nod][i];
        if(cuplaj(r[vecin])){
            l[nod]=vecin;
            r[vecin]=nod;
            return 1;
        }
    }
    return 0;
}
int main () {
    fin>>n>>m>>nr;
    for(i=1;i<=nr;i++){
        fin>>x>>y;
        Lista[x].push_back(y);
    }
    do{
        memset(Marcat,0,sizeof(Marcat));
        ok=0;
        for(i=1;i<=n;i++){
            if(!l[i])
                ok=max(ok,cuplaj(i));
        }
    }while(ok);
    nr=0;
    for(i=1;i<=n;i++)
        if(l[i])
            nr++;
    fout<<nr<<"\n";
    for(i=1;i<=n;i++)
        if(l[i])
            fout<<i<<" "<<l[i]<<"\n";
    return 0;
}