#include <iostream>
#include <fstream>
#include <vector>

const int MAXN = 1e4 + 5;

using namespace std;

ifstream in("cuplaj.in");
ofstream out("cuplaj.out");

vector<int>graf[MAXN];
int n,m,boss_left[MAXN],boss_right[MAXN];
int cnt_cuplaj = 0;

void afis(){
    cout<<"cuplajul este : \n";
    for(int i = 1; i <= n; i++){
        if(boss_right[i])
            cout<<i<<" "<<boss_right[i]<<endl;
    }
    cout<<"======="<<endl;
}
bool cuplaj(int nod){
    for(auto vecin : graf[nod]){
        if(boss_left[vecin] == 0){
            boss_left[vecin] = nod;
            boss_right[nod] = vecin;
            cnt_cuplaj++;
            return true;
        }
    }
    for(auto vecin : graf[nod]){
        if(nod != boss_right[vecin] && cuplaj(boss_right[vecin])){
            boss_left[vecin] = nod;
            boss_right[nod] = vecin;
            return true;
        }
    }
    return false;
}

int main()
{
    int muchii;
    in>>n>>m>>muchii;

    for(int i = 1; i <= muchii; i++){
        int x,y;
        in>>x>>y;
        graf[x].push_back(y);
    }
    while(true){
        int copie = cnt_cuplaj;
        for(int i = 1; i <= n; i++)
            cuplaj(i);
        if(copie == cnt_cuplaj)
            break;
    }
    int cnt = 0;
    for(int i = 1; i <= n; i++)
        if(boss_left[i])
            cnt++;
    out<<cnt<<"\n";
    for(int i = 1; i <= n; i++)
        if(boss_left[i])
            out<<i<<" "<<boss_left[i]<<"\n";
    return 0;
}