#include <fstream>
#include <vector>

using namespace std;

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

const int nmax = 10005;
int n, m, i, j, x, y, k, ok, sol;
int lft[nmax], rgt[nmax], viz[nmax];
vector <int> ls[nmax];

int pairup(int x) {
    if (viz[x])
        return 0;
    int l = ls[x].size(), i, y;
    viz[x] = 1;
    for (i = 0; i < l; i++) {
        y = ls[x][i];
        if (rgt[y] == 0) {
            lft[x] = y;
            rgt[y] = x;
            return 1;
        }
    }

    for (i = 0; i < l; i++) {
        y = ls[x][i];
        if (pairup(rgt[y])) {
            lft[x] = y;
            rgt[y] = x;
            return 1;
        }
    }

    return 0;
}

int main() {
    f >> n >> m >> k;
    while (k--) {
        f >> x >> y;
        ls[x].push_back(y);
    }

    ok = 1;
    while (ok) {
        ok = 0;
        for (i = 1; i <= n; i++)
            viz[i] = 0;
        for (i = 1; i <= n; i++)
            if (lft[i] == 0)
                ok |= pairup(i);
    }

    for (i = 1; i <= n; i++)
        if (lft[i]) sol++;

    g << sol << '\n';
    for (i = 1; i <= n; i++)
        if (lft[i])
            g << i << ' ' << lft[i] << '\n';

    return 0;
}