#include <bits/stdc++.h>
#define MAX 10005
using namespace std;

int n, m, e, x, y, nrCupl, cuplL[MAX], cuplR[MAX];
vector<int> l[MAX];
bool change, viz[MAX];

bool cuplaj(int x) {
	if (viz[x])
		return 0;
	viz[x] = 1;

	for (int i = 0; i < l[x].size(); ++i)
		if (!cuplR[l[x][i]]) {
			cuplL[x] = l[x][i];
			cuplR[l[x][i]] = x;
			return 1;
		}

	for (int i = 0; i < l[x].size(); ++i)
		if (cuplaj(cuplR[l[x][i]])) {
			cuplL[x] = l[x][i];
			cuplR[l[x][i]] = x;
			return 1;
		}

	return 0;
}

int main() {
	freopen("cuplaj.in", "r", stdin);
	freopen("cuplaj.out", "w", stdout);
	cin >> n >> m >> e;
	for (int i = 0; i < e; ++i) {
		cin >> x >> y;
		l[x].push_back(y);
	}

	change = 1;
	while (change) {
		change = 0;
		memset(viz + 1, 0, n);
		for (int i = 1; i <= n; ++i)
			if (!cuplL[i])
				change |= cuplaj(i);
	}

	for (int i = 1; i <= n; ++i)
		if (cuplL[i])
			++nrCupl;
	cout << nrCupl << "\n";
	for (int i = 1; i <= n; ++i)
		if (cuplL[i])
			cout << i << " " << cuplL[i] << "\n";

	return 0;
}