#include<stdio.h>
#include<vector>
using namespace std;
vector<int>g[10213];
vector<int>::iterator it;
int m,n,p,i,j,k,l[10213],r[10213],mn;
bool ok,f[10213];
bool go(int x)
{
	if(f[x])return 0;
	f[x]=1;
	vector<int>::iterator it;
	for(it=g[x].begin();it!=g[x].end();++it)
		if(!r[*it])
		{
			l[x]=*it;
			r[*it]=x;
			return 1;
		}
	for(it=g[x].begin();it!=g[x].end();++it)
		if(go(r[*it]))
		{
			l[x]=*it;
			r[*it]=x;
			return 1;
		}
	return 0;
}
int main()
{
	freopen("cuplaj.in","r",stdin);
	freopen("cuplaj.out","w",stdout);
	scanf("%d%d%d",&n,&m,&p);mn=max(m,n);
	for(i=0;i<p;++i)
	{
		scanf("%d%d",&j,&k);
		g[j].push_back(k);
	}
	ok=1;
	while(ok)
	{
		ok=0;
		for(i=1;i<=mn;++i)f[i]=0;
		for(i=1;i<=n;++i) if(!l[i]) if(go(i))ok=1;
	}
	k=0;
	for(i=1;i<=n;++i)if(l[i])++k;
	printf("%d\n",k);
	for(i=1;i<=n;++i)if(l[i]) printf("%d %d\n",i,l[i]);
	return 0;
}