#include<algorithm>
#include<bitset>
#include<cmath>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<ctime>
#include<deque>
#include<fstream>
#include<iomanip>
#include<iostream>
#include<map>
#include<queue>
#include<set>
#include<stack>
#include<unordered_map>
#include<unordered_set>
#include<utility>
#include<vector>

using namespace std;

#ifdef HOME
const string inputFile = "input.txt";
const string outputFile = "output.txt";
#else
const string problemName = "cuplaj";
const string inputFile = problemName + ".in";
const string outputFile = problemName + ".out";
#endif

const int NMAX = 10000 + 5;

int N, M, E, cnt;
vector<int> V[NMAX];
int L[NMAX];
int R[NMAX];
bitset<NMAX> viz;

int pair_up(int x) {
    if(viz[x])
        return 0;

    viz[x] = 1;

    for(auto y : V[x])
        if((!R[y]) || (pair_up(R[y]))) {
            L[x] = y;
            R[y] = x;
            return 1;
        }

    return 0;
}

int main() {
    int i, x, y, ok;

#ifndef ONLINE_JUDGE
    freopen(inputFile.c_str(), "r", stdin);
    freopen(outputFile.c_str(), "w", stdout);
#endif

    scanf("%d%d%d", &N, &M, &E);

    while(E--) {
        scanf("%d%d", &x, &y);
        V[x].push_back(y);
    }

    do {
        ok = 0;
        viz = 0;

        for(i = 1; i <= N; i++)
            if(!L[i])
                ok |= pair_up(i);
    } while(ok);

    for(i = 1; i <= N; i++)
        if(L[i])
            cnt++;

    printf("%d\n", cnt);

    for(i = 1; i <= N; i++)
        if(L[i])
            printf("%d %d\n", i, L[i]);

    return 0;
}