#include <iostream>
#include <fstream>
#include <vector>
#include <queue>
#include <set>
#include <stack>
#include <cmath>
#include <cstring>
#include <algorithm>
#include <iomanip>

#define PI 3.1415
#define INF 0x3f3f3f3f
#define NMax 20005
using namespace std;
ifstream f("cuplaj.in");
ofstream g("cuplaj.out");

int n,m,e,x,y,ANS;
int viz[NMax],vL[NMax],vR[NMax];
vector<int> G[NMax];

int cuplaj(int nod){
    if(viz[nod])
        return 0;
    viz[nod] = 1;
    for(int i = 0; i < G[nod].size(); ++i){
        if(vL[G[nod][i]] == 0 || cuplaj(vL[G[nod][i]])){
            vL[G[nod][i]] = nod;
            vR[nod] = G[nod][i];
            return 1;
        }
    }
    return 0;
}
int main()
{
    f >> n >> m >> e;
    for(int i = 1; i <= e; ++i){
        f >> x >> y;
        G[x].push_back(y + n);
    }
    int ok = 1;
    while(ok){
        ok = 0;
        memset(viz,0,sizeof(viz));
        for(int i = 1; i <= n; ++i){
            if(vR[i] == 0){
                if(cuplaj(i)){
                    ok = 1;
                    ANS++;
                }
            }
        }
    }
    g << ANS << '\n';
    for(int i = 1; i <= n; ++i){
      //  g << i << '\n';
        if(vR[i])
            g << i << ' ' << vR[i] - n << '\n';
    }
    return 0;
}