#include <vector>
#include <string> 
#include <set> 
#include <map> 
#include <queue> 
#include <bitset> 
#include <stack>
#include <list>

#include <numeric> 
#include <algorithm> 

#include <cstdio>
#include <fstream>
#include <iostream> 
#include <sstream> 
#include <iomanip>

#include <cctype>
#include <cmath> 
#include <ctime>
#include <cassert>

using namespace std;

#define LL long long
#define PII pair <int, int>
#define VB vector <bool>
#define VI vector <int>
#define VD vector <double>
#define VS vector <string>
#define VPII vector <pair <int, int> >
#define VVI vector < VI >
#define VVB vector < VB >

#define FORN(i, n) for(int i = 0; i < (n); ++i)
#define FOR(i, a, b) for(int i = (a); i <= (b); ++i)
#define FORD(i, a, b) for(int i = (a); i >= (b); --i)
#define FORI(it, X) for(__typeof((X).begin()) it = (X).begin(); it !=(X).end(); ++it) 
#define REPEAT do{ 
#define UNTIL(x) }while(!(x)); 

#define SZ size()
#define BG begin() 
#define EN end() 
#define CL clear()
#define X first
#define Y second
#define RS resize
#define PB push_back
#define MP make_pair
#define ALL(x) x.begin(), x.end()

#define IN_FILE "cuplaj.in"
#define OUT_FILE "cuplaj.out"

ifstream fin(IN_FILE);
ofstream fout(OUT_FILE);

int n1, n2, m, sol = 0;
VVI g;
VI l, r, level;
VB was;

bool Bf()
{
	bool ans = false;
	fill(ALL(level), 0);
	fill(ALL(was), false);
	queue<int> fifo;
	FOR(i, 1, n1) 
		if (!l[i]) 
		{
			fifo.push(i);
			level[i] = 1;
		}
	while (!fifo.empty())
	{
		int node = fifo.front();
		fifo.pop();
		if (node <= n1)
		{
			//Left node
			FORN(i, g[node].SZ)
			{
				int next = g[node][i];
				if (level[next]) continue;
				level[next] = level[node] + 1;
				fifo.push(next);
			}
		}
		else
		{
			//Right node
			if (!r[node - n1]) 
			{
				ans = true;
				continue;
			}
			int next = r[node - n1];
			level[next] = level[node] + 1;
			fifo.push(next);
		}
	}
	return ans;
}

bool Df(int node, int parent)
{
	if (was[node]) return false;
	was[node] = true;
	if (level[node] == 1) 
	{
		l[node] = parent - n1;
		return true;
	}
	if (node <= n1)
	{
		//Left node
		if (Df(l[node] + n1, node))
		{
			l[node] = parent - n1;
			return true;
		}
	}
	else
	{
		//Right node
		FORN(i, g[node].SZ)
		{
			int next = g[node][i];
			if (level[next] == level[node] - 1)
			{
				if (Df(next, node))
				{
					r[node - n1] = next;
					return true;
				}
			}
		}
	}
	return false;
}

void HopcroftKarp()
{
	while (Bf())
	{
		fill(ALL(was), false);
		FOR(i, 1, n2)
			if (!r[i] && level[i + n1]) 
				if (Df(i + n1, -1)) ++sol;
	}
}

int main()
{
	//Read data
	fin >> n1 >> n2 >> m;
	g.RS(n1 + n2 + 1);
	FOR(i, 1, m)
	{
		int x, y;
		fin >> x >> y;
		g[x].PB(y + n1);
		g[y + n1].PB(x);
	}
	fin.close();

	//Solve
	l.RS(n1 + 1);
	r.RS(n2 + 1);
	level.RS(n1 + n2 + 1);
	was.RS(n1 + n2 + 1);
	HopcroftKarp();

	//Write data
	fout << sol << endl;
	FOR(i, 1, n1)
		if (l[i]) fout << i << " " << l[i] << '\n';
	fout.close();

	return 0;
}