#include <string.h>

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

const int MAXN = 10005;

vector <int> G[MAXN];

int l[MAXN], r[MAXN], viz[MAXN];

/// Returns true if found a way to pair it up
bool pairup(const int n) {
    if (viz[n])
        return 0;
    viz[n] = 1;

    /// Try to pair with neighbour which doesn't already have pair
    for(const int i : G[n]) {
        if (r[i] == 0) {
            l[n] = i;
            r[i] = n;
            return 1;
        }
    }

    /// Try to free up neighbour and then make pair
    for(const int i : G[n]) {
        if (pairup(r[i])) {
            l[n] = i;
            r[i] = n;
            return 1;
        }
    }
    return 0;
}

int main(void) {
    ifstream in("cuplaj.in");
    ofstream out("cuplaj.out");

    int n, m, cnt_edges;
    in >> n >> m >> cnt_edges;
    while (cnt_edges --) {
        int x, y;
        in >> x >> y;
        G[x].push_back(y);
    }

    bool change = true;
    while (change) {
        change = false;
        memset(viz, 0, sizeof(viz)); // RESET VIZ

        for(int i = 1; i <= n; i++) {
            if (l[i] == 0) /// If I has no pair
                change |= pairup(i);
        }
    }

    int cuplaj = 0;
    for(int i = 1; i <= n; i++) {
        cuplaj += (l[i] > 0);
    }

    out << cuplaj << '\n';
    for(int i = 1; i <= n; i++)
        if (l[i] > 0)
            out << i << ' ' << l[i] << '\n';

    return 0;
}