/*
 Cat timp S-A EFECTUAT CUPLARE
	pentru fiecare v din V1
		daca (!M1[v] ) atuci cupleaza(v);

unde M1(v) = suprafata cuplata cu V
	 M2(x) = lungimea?? cuplata cu Suprafata x ?????

bool cupleaza(v) 
	daca  a fost folosit v atuci return false;
	pentru fiecare x adiacent v executa 
		daca (!M2[x]) atunci 
			M1[v] = x si M2[x] = v;
			return true
	pentru fiecare x adiacent v executa
		daca ( cupleaza( M2[x] )  )
			M1[v] = x; M2[x] = v;
			return true;

*/


#include <iostream>
#include <fstream>
#include <string.h>
#include <vector>
//#include <queue>
//#include <algorithm>

using namespace std;
const int nmax = 10001;

vector <int> a[nmax], b[nmax];
int ap[nmax], bp[nmax];									// pairs of the nodes
char folosit[nmax];
int la,lb;

bool cuplare(int v);

int main(){
	freopen("cuplaj.in", "r", stdin);
	freopen("cuplaj.out", "w", stdout);
	int m,x,y;
	scanf("%d %d %d", &la, &lb, &m);
	for (int i = 0; i < m; i++) {
		scanf("%d %d", &x, &y);
		a[x].push_back(y);
	}

	// initial
	int nrCuplaje = 0;
	memset(ap, 0, 4 * (la + 2));
	memset(bp, 0, 4 * (lb + 2));
	// apgorimul
	bool changed = true;
	while (changed) {
		changed = false;
		memset(folosit, 0, la + 1);
		for (int i = 1; i <= la; i++) {
			if (!ap[i]) {
				if (cuplare(i)) {
					changed = true;
					nrCuplaje++;
				}
			}
		}
	}

	printf("%d \n", nrCuplaje);
	for (int i = 1; i <= la; i++)
		if (ap[i] != 0 )	printf("%d %d\n", i, ap[i]);
	fclose(stdin);
	fclose(stdout);
	return 0;
}


bool cuplare(int v) {
	if (folosit[v] != 0) return false;
	
	folosit[v] = 1;
	for (int ii = 0; ii < a[v].size(); ii++)
		if (bp[a[v][ii]] == 0) {
			ap[v] = a[v][ii];
			bp[a[v][ii]] = v;
			return true;
		}
	for (int ii = 0; ii < a[v].size(); ii++)
		if (cuplare(ap[a[v][ii]])) {
			ap[v] = a[v][ii];
			bp[a[v][ii]] = v;
			return true;
		}
	return false;
	
}