//Marius
#include <cstdio>
#include <vector>
#include <algorithm>
using namespace std;

const char iname[] = "cuplaj.in";
const char oname[] = "cuplaj.out";

#define MAXN  10005
#define FOR(i, a, b)  for (int i = (int)(a); i <= (int)(b); ++ i)
#define FORI(i, V)    for (vector <int>::iterator i = (V).begin(); i != (V).end(); ++ i)

vector <int> G[MAXN];

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


int pairup(const int n)
{
	if (u[n])  return 0;
	u[n] = 1;
	FORI (i, G[n]) if (!r[*i]) {
		l[n] = *i;
		r[*i] = n;
		return 1;
	}
	FORI (i, G[n]) if (pairup(r[*i])) {
		l[n] = *i;
		r[*i] = n;
		return 1;
	}
	return 0;
}

int main(void)
{
	freopen(iname, "r", stdin);
	freopen(oname, "w", stdout);

	int n, m, cnt_edges;
	scanf("%d %d %d", &n, &m, &cnt_edges);

	for (; cnt_edges --; )
	{
		int x, y;
		scanf("%d %d", &x, &y);
		G[x].push_back(y);
	}
	for (int change = 1; change; )
	{
		change = 0;
		memset(u, 0, sizeof(u));
		FOR (i, 1, n) if (!l[i])
			change |= pairup(i);
	}
	int cuplaj = 0;
	FOR (i, 1, n)  cuplaj += (l[i] > 0);
	printf("%d\n", cuplaj);
	FOR (i, 1, n) if (l[i] > 0)
		printf("%d %d\n", i, l[i]);

	return 0;
}