#include <stdio.h>
#include <vector>

#define maxdim 100005

using namespace std;

int n, m, edges;
int viz[maxdim], l[maxdim], r[maxdim];
vector<int> G[maxdim];

bool cuplaj(int nod) {
	if (viz[nod]) {
		return false;
	}
	viz[nod] = true;
	
	for (int other : G[nod]) {
		if (!r[other]) {
			l[nod] = other;
			r[other] = nod;
			return true;
		}
	}
	
	for (int other : G[nod]) {
		if (cuplaj(r[other])) {
			l[nod] = other;
			r[other] = nod;
			return true;
		}
	}
	
	return false;
}

int main() {
	
	freopen("cuplaj.in", "r", stdin);
	freopen("cuplaj.out", "w", stdout);
	
	scanf("%d %d %d", &n, &m, &edges);
	for (int i = 1; i <= edges; ++i) {
		int x, y; scanf("%d %d", &x, &y);
		G[x].push_back(y);
	}
	
	int updated = 1;
	while (updated) {
		updated = 0;
		for (int i = 1; i <= n; ++i) {
			viz[i] = 0;
		}
		for (int i = 1; i <= n; ++i) {
			if (!l[i]) {
				updated |= cuplaj(i);
			}
		}
	}
	
	int cardinal = 0;
	for (int i = 1; i <= n; ++i) {
		cardinal += l[i] != 0;
	}
	printf("%d\n", cardinal);
	for (int i = 1; i <= n; ++i) {
		if (l[i] != 0) {
			printf("%d %d\n", i, l[i]);
		}
	}

	return 0;
}