#include <fstream>
#include <queue>
#include <vector>
#include <cstring>
 
using namespace std;
 
static const int MAXN = 10009;
int n, m;
vector<int> G[MAXN];
int matchForL[MAXN];
int matchForR[MAXN];
bool u[MAXN];
int dist[MAXN];

void bfs()
{
	int nod;
	memset(u, 0, sizeof u);
	memset(dist, 0x3F, sizeof dist);
	queue<int> q;
	for(int i = 1; i <= n; i++)
	{
		if(!matchForL[i])
		{
			u[i] = true;
			q.push(i);
			dist[i] = 0;
		}
	}
	while(!q.empty())
	{
		nod = q.front();
		q.pop();
		for(int i = 0, l = G[nod].size(); i < l; i++)
		{
			int vec = matchForR[G[nod][i]];
			if(vec && !u[vec])
			{
				dist[vec] = dist[nod] + 1;
				u[vec] = true;
				q.push(vec);
			}
		}
	}
}

bool dfs(int who)
{
	u[who] = true;
	for(int i = 0, l = G[who].size(); i < l; i++)
	{
		int vec = matchForR[G[who][i]];
		if(!vec || (!u[vec] && dist[vec] == dist[who] + 1 && dfs(vec)))
		{
			matchForL[who] = G[who][i];
			matchForR[G[who][i]] = who;
			return true;
		}
	}
	return false;
}
 
int main()
{
    int 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(y);
    }
    f.close();
    bool ok = true;
    do
    {
        ok = false;
        bfs();
		memset(u, 0, sizeof u);
		for(int i = 1; i <= n; i++)
		{
			if(!matchForL[i])
			{
				ok = dfs(i) || ok;
			}
		}
    } while(ok);
    vector<pair<int, int> > ans;
    for(int i = 1; i <= n; i++)
    {
        if(matchForL[i])
        {
            ans.push_back(pair<int, int>(i, matchForL[i]));
        }
    }
    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;
}