# 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],l[DIM],r[DIM],nl,nr,m,x,y,i,ok;
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(r[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>>nl>>nr>>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(int i=1;i<=nl;i++)
            if(!r[i])
                ok=max(ok,cuplaj(i));
    }
    m=0;
    for(int i=1;i<=nl;i++)
        if(r[i])
            m++;
    fout<<m<<"\n";
    for(i=1;i<=nl;i++)
        if(r[i])
            fout<<i<<" "<<r[i]<<"\n";
    return 0;
}