#include<bits/stdc++.h>
using namespace std;
ifstream in("cuplaj.in");
ofstream out("cuplaj.out");
const int Nmax = 10001;
vector<int> L[Nmax];
int l[Nmax],r[Nmax],mk[Nmax];
int n,m,q;
int cup(int x){
    if(mk[x]) return 0;
    mk[x]=1;
    for(auto p : L[x]){
        if(r[p]==0 || cup(r[p])){
            l[x]=p;
            r[p]=x;
            return 1;
        }
    }
    return 0;
}
int main(){
    in>>n>>m>>q;
    for(int i=1;i<=q;i++){
        int x,y;
        in>>x>>y;
        L[x].push_back(y);
    }
    for(int i=1;i<=n;i++){
        if(!l[i]){
            fill_n(mk,n,0);
            mk[0]+=cup(i);
        }
    }
    out<<mk[0]<<'\n';
    for(int i=1;i<=n;i++){
        if(l[i]) out<<i<<' '<<l[i]<<'\n';
    }
    return 0;
}