#include <iostream>
#include <cstdio>
#include <vector>
#include <bitset>
#define MAXN 10050

using namespace std;

int l[MAXN], r[MAXN], n, m, e;
vector<int> graf[MAXN];
bitset<MAXN> viz;

void citire()
{
	int x, y;
    scanf("%d %d %d\n", &n, &m, &e);
    for (int i = 0; i < e; i++) {
        scanf("%d %d", &x, &y);
		graf[x].push_back(y);
    }
}

int cupleaza(int nod)
{
    if (viz[nod]) return false;
    viz[nod] = 1;
    for (int i = 0, t = graf[nod].size(); i < t; i++) {
        int y = graf[nod][i];
        if (!r[y] || cupleaza(r[y])) {
			l[nod] = y;
			r[y] = nod;
			return true;
        }
    }
    return false;
}

void solve()
{
    int ok;
    for (ok = 1; ok; ) {
		viz = 0;
		ok = 0;
		for (int i = 1; i <= n; i++)
			if (!l[i])
				ok |= cupleaza(i);
    }
}

void afisare()
{
    int cnt = 0;
    for (int i = 1; i <= n; i++) cnt += (l[i]!=0);
    printf("%d\n", cnt);
    for (int i = 1; i <= n; i++)
		if (l[i])
			printf("%d %d\n", i, l[i]);
}

int main()
{
    freopen("cuplaj.in", "r", stdin);
    freopen("cuplaj.out", "w", stdout);

	citire();
	solve();
	afisare();

    return 0;
}