#include <algorithm>
#include <cstdio>
#include <cstring>

using namespace std;

inline int next_int() {
	int n = 0;
	char c = getchar_unlocked();
	while (!('0' <= c && c <= '9')) {
		c = getchar_unlocked();
	}
	while ('0' <= c && c <= '9') {
		n = n * 10 + c - '0';
		c = getchar_unlocked();
	}
	return n;
}

const int V = 10000 + 2;
const int E = 100000 + 2;

int ec, eb[V], en[E], et[E];
int n, m, XY[V], YX[V];
bool seen[V];

bool dfs(int u) {
	if (seen[u]) {
		return false;
	}
	seen[u] = true;
	for (int e = eb[u]; e != -1; e = en[e]) {
		int v = et[e];
		if (YX[v] == -1) {
			XY[u] = v;
			YX[v] = u;
			return true;
		}
	}
	for (int e = eb[u]; e != -1; e = en[e]) {
		int v = et[e];
		if (dfs(YX[v])) {
			XY[u] = v;
			YX[v] = u;
			return true;
		}
	}
	return false;
}

int main() {
	//freopen("cuplaj.in", "r", stdin);
	//freopen("cuplaj.out", "w", stdout);
	memset(eb, -1, sizeof eb);
	memset(XY, -1, sizeof XY);
	memset(YX, -1, sizeof YX);
	int n = next_int();
	int m = next_int();
	int e = next_int();
	for (int i = 0; i < e; i++) {
		int u = next_int();
		int v = next_int();
		et[ec] = v;
		en[ec] = eb[u];
		eb[u] = ec++;
	}
	int ans = 0;
	for (bool done = false; !done;) {
		done = true;
		memset(seen, 0, sizeof seen);
		for (int i = 1; i <= n; i++) {
			if (XY[i] == -1 && dfs(i)) {
				ans++;
				done = false;
			}
		}
	}
	printf("%d\n", ans);
	for (int i = 1; i <= n; i++) {
		if (XY[i] != -1) {
			printf("%d %d\n", i, XY[i]);
		}
	}
	return 0;
}