#include <fstream>
#include <vector>
#include <cstring>
#include <algorithm>
using namespace std;

#define MAXN 20000

ifstream fin("cuplaj.in");
ofstream fout("cuplaj.out");

int used[MAXN], l[MAXN], r[MAXN], n, m, muchii, rez;
vector<int> g[MAXN];

int pairup(int nod) {
    int i;
    if (used[nod]) return 0;
    used[nod] = 1;
    for (i = 0; i < g[nod].size(); ++i) {
        if (!r[g[nod][i]]) {
            r[g[nod][i]] = nod;
            l[nod] = g[nod][i];
            return 1;
        }
    }
    for(i = 0; i < g[nod].size(); ++i) {
        if (pairup(r[g[nod][i]])) {
            r[g[nod][i]] = nod;
            l[nod] = g[nod][i];
            return 1;
        }
    }
    return 0;
}

int main() {
    int i, x, y, change = 1;
    fin >> n >> m >> muchii;
    for (i = 1; i <= muchii; ++i) {
        fin >> x >> y;
        g[x].push_back(y);
    }
    for (change = 1; change; ) {
        change = 0;
        memset(used, 0, sizeof(used));
        for (i = 1; i <= n; ++i)
            if (!l[i])
                if (pairup(i))
                    change = 1;
    }
    for (i = 1; i <= n; ++i) if (l[i] > 0) ++rez;
    fout << rez << "\n";
    for (i = 1; i <= n; ++i)
        if (l[i] > 0)
            fout << i << " " << l[i] << "\n";
    fout.close();
    return 0;
}