#include <fstream>
#include <vector>

using namespace std;

static const int MAXN = 20009;
vector<int> G[MAXN];
int match[MAXN];
bool u[MAXN];

bool match_it(int who)
{
	int vec;
	bool success = false;
	u[who] = true;
	for(int i = 0, l = G[who].size() && !success; i < l; i++)
	{
		vec = G[who][i];
		if(!u[vec] && vec != match[who]) // edge is white and node was not used
		{
			if(!match[vec]) //end of the ride
			{
				success = true;
			}
			else
			{
				success = match_it(match[vec]); //go black
			}
			if(success)
			{
				match[who] = vec;
				match[vec] = who;
			}
		}
	}
	return success;
}

int main()
{
	int n, m, e, x, y;
	ifstream f("cuplaj.in");
	f >> n >> m >> e;
	for(int i = 0; i < e; i++)
	{
		f >> x >> y;
		G[x].push_back(n + y);
		G[n + y].push_back(x);
	}
	f.close();
	for(int i = 1; i <= n + m; i++)
	{
		if(!match[i])
		{
			memset(u, 0, sizeof u);
			match_it(i);
		}
	}
	vector<pair<int, int> > ans;
	for(int i = 1; i <= n; i++)
	{
		if(match[i])
		{
			ans.push_back(pair<int, int>(i, match[i] - n));
		}
	}
	ofstream g("cuplaj.out");
	g << ans.size() << '\n';
	for(int i = 0, l = ans.size(); i < l; i++)
	{
		g << ans[i].first << ' ' << ans[i].second << '\n';
	}
	g.close();
	return 0;
}