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

using namespace std;

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

const int NMAX = 10000 + 1;

int n, m, k;
bool vizitat[NMAX];
vector <int> graf[NMAX];
int a[NMAX], b[NMAX];

void citeste() {
    int a, b;

    f >> n >> m >> k;
    for (int i = 1; i <= k; i++) {
        f >> a >> b;
        graf[a].push_back(b);
    }
}

bool dfs(int nod) {
    if (vizitat[nod] == true) return false;
    vizitat[nod] = true;

    int l, fiu;
    vizitat[nod] = true;

    l = graf[nod].size();
    for (int i = 0; i < l; i++) {
        fiu = graf[nod][i];
        if (!a[fiu]) {
            a[fiu] = nod;
            b[nod] = fiu;
            return true;
        }
    }

    for (int i = 0; i < l; i++) {
        fiu = graf[nod][i];
        if (dfs(a[fiu])) {
            a[fiu] = nod;
            b[nod] = fiu;
            return true;
        }
    }

    return false;
}

void cuplaj() {
    bool done = false;

    while(!done) {
        done = true;
        for (int i = 1; i <= n; i++) vizitat[i] = false;
        for (int i = 1; i <= n; i++)
            if (!b[i]) {
                if (dfs(i)) done = false;
            }
    }
}

void scrie() {
    int nr = 0;
    for (int i = 1; i <= n; i++)
        if (b[i]) nr++;
    g << nr << '\n';
    for (int i = 1; i <= n; i++)
        if (b[i]) g << i << ' ' << b[i] << '\n';
}

int main() {
    citeste();
    cuplaj();
    scrie();
}