# 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],stanga[DIM],dreapta[DIM],r,l,m,n,x,y,i,ok;
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(stanga[vecin]==0){
            stanga[vecin]=nod;
            dreapta[nod]=vecin;
            return 1;
        }
    }
    for(int i=0;i<Lista[nod].size();i++){
        int vecin=Lista[nod][i];
        if(cuplaj(stanga[vecin])){
            stanga[vecin]=nod;
            dreapta[nod]=vecin;
            return 1;
        }
    }
    return 0;
}
int main () {
    fin>>l>>r>>m;
    for(i=1;i<=m;i++){
        fin>>x>>y;
        Lista[x].push_back(y);
    }
    ok=1;
    while(ok){
        ok=0;
        memset(Marcat,0,sizeof(Marcat));
        for(i=1;i<=l;i++)
            if(!dreapta[i])
                ok=max(ok,cuplaj(i));
    }
    for(i=1;i<=l;i++)
        if(dreapta[i])
            n++;
    fout<<n<<"\n";
    for(i=1;i<=l;i++)
        if(dreapta[i])
            fout<<i<<" "<<dreapta[i]<<"\n";
    return 0;
}