#include <iostream>
#include <fstream>
#include <vector>
#include <string.h>
using namespace std;

#define NMAX 10001

vector <int> v[NMAX];
int st[NMAX], dr[NMAX], viz[NMAX];

int cupleaza(int nod) {
    viz[nod] = 1;
    for (const int x : v[nod]) {
        if (dr[x] == 0) {
            st[nod] = x;
            dr[x] = nod;
            return 1;
        }
        else if (viz[dr[x]] == 0) {
            if (cupleaza(dr[x])) {
                st[nod] = x;
                dr[x] = nod;
                return 1;
            }
        }
    }
    return 0;
}

int hopcroft_karp(const int n) {
    int ok;
    do {
        ok = 0;
        memset(viz, 0, sizeof(viz));
        for (int i = 1; i <= n; i++) {
            if (viz[i] == 0 && st[i] == 0)
                ok = ok | cupleaza(i);
        }
    } while (ok);

    int nr = 0;
    for (int i = 1; i <= n; i++) {
        nr += (st[i] != 0);
    }
    return nr;
}

int main()
{
    int n, m, e;
    ifstream f("cuplaj.in");
    ofstream g("cuplaj.out");
    f >> n >> m >> e;
    for (int i = 1; i <= e; i++) {
        int x, y;
        f >> x >> y;
        v[x].push_back(y);
    }
    f.close();

    int nr = hopcroft_karp(n);
    g << nr << '\n';
    for (int i = 1; i <= n; i++) {
        if (st[i]) {
            g << i << " " << st[i] << '\n';
        }
    }
    g.close();
    return 0;
}