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