#include<cstdio>
#include<cstring>
#include<cstdlib>

#include<vector>
using std::vector;

int inc[20005];
int nc=0;
bool seen[20005];

vector<int> v[20005];

bool dfs (int i)
{
	if(seen[i])
		return 0;

	seen[i]=1;

	for(vector<int>::iterator it=v[i].begin();it!=v[i].end();it++)
		if(!inc[*it] || dfs (inc[*it])){
			if(!inc[i])
				nc++;
			inc[*it]=i;
			inc[i]=*it;
			return 1;
		}

	return 0;
}

int main()
{
	freopen ("cuplaj.in","r",stdin);
#ifdef INFOARENA
	freopen ("cuplaj.out","w",stdout);
#endif

	int n,m,e;
	scanf ("%d%d%d\n",&n,&m,&e);
	char s[100];
	for(int i=0;i<e;i++){
		int x,y;
		gets (s);
		x=atoi (s);
		y=atoi (strchr (s,' ')+1);
		y+=n;
		
		v[x].push_back (y);
	}

	for(int i=1;i<=n;i++){
		memset (seen, 0, sizeof seen);
		dfs (i);
	}

	printf ("%d\n",nc);
	for(int i=1;i<=n;i++)
		if(inc[i])
			printf ("%d %d\n",i,inc[i]-n);

	return 0;
}