#include <stdio.h>
#include <vector>
#include <list>
#define pb push_back
#define mp make_pair
using namespace std;

int n, m, cuplaj;
vector< list<int> > vecini;
vector<bool> sel, sel2;
vector<int> t, nivel;
vector< pair<int, int> > muchii;

void read();
void solve();
void write();
void dfs(int);

int main()
{
	read();
	solve();
	write();
	return 0;
}

void dfs(int nod)
{
	sel[nod] = 1;
	list<int>::iterator i, sfarsit = vecini[nod].end();
	for (i = vecini[nod].begin(); i != sfarsit; ++i)
	{
		if (!sel[*i])
		{
			t[*i] = nod;
			nivel[*i] = nivel[nod] + 1;
			dfs(*i);
		}
	}
	if (t[nod] && !sel2[nod] && !sel2[t[nod]])
	{
		sel2[nod] = sel2[t[nod]] = 1;
		int x = nod, y = t[nod];
		if (x > n)
		{
			muchii[++cuplaj] = mp(y, x - n);
		}
		else
		{
			muchii[++cuplaj] = mp(x, y - n);
		}
	}
}

void solve()
{
	muchii.reserve(m + n + 1);
	cuplaj = 0;
	int i;
	for (i = 1; i <= n + m; ++i)
	{
		if (!sel[i])
		{
			dfs(i);
		}
	}
}

void write()
{
	int i;
	FILE *fout = fopen("cuplaj.out", "w");
	fprintf(fout, "%d\n", cuplaj);
	for (i = 1; i <= cuplaj; ++i)
	{
		fprintf(fout, "%d %d\n", muchii[i].first, muchii[i].second);
	}
	fclose(fout);
}

void read()
{
	int i, e, x, y;
	FILE *fin = fopen("cuplaj.in", "r");
	fscanf(fin, "%d%d%d", &n, &m, &e);
	vecini.resize(n + m + 1);
	sel.resize(n + m + 1, 0);
	sel2.resize(n + m + 1, 0);
	t.resize(n + m + 1, 0);
	nivel.resize(n + m + 1, 1);
	for (i = 1; i <= e; ++i)
	{
		fscanf(fin, "%d%d", &x, &y);
		vecini[x].pb(y + n);
		vecini[y+n].pb(x);
	}
	fclose(fin);
}