#include<stdio.h>

int v[10100],ver[100100],leg[100100],start[10100],s[10100],d[10100];

int match(int nod)
{
	if(v[nod])
		return 0;
	v[nod]=1;
	int t=start[nod];
	while(t)
	{
		if(!d[ver[t]]||match(d[ver[t]]))
		{
			s[nod]=ver[t];
			d[ver[t]]=nod;
			return 1;
		}
		t=leg[t];
	}
	return 0;
}

int main()
{
	int e,n,m,x,y,ok,c=0,i,q=0;
	freopen("cuplaj.in","r",stdin);
	freopen("cuplaj.out","w",stdout);
	scanf("%d %d %d",&n,&m,&e);
	while(e--)
	{
		scanf("%d %d",&x,&y);
		ver[++q]=y;
		leg[q]=start[x];
		start[x]=q;
	}
	ok=1;
	while(ok)
	{
		for(i=1;i<=n;i++)
			v[i]=0;
		ok=0;
		for(i=1;i<=n;i++)
			if(!s[i])
				if(match(i))
				{
					c++;
					ok=1;
				}	
	}
	printf("%d\n",c);
	for(i=1;i<=n;i++)
		if(s[i])
			printf("%d %d\n",i,s[i]);
	return 0;
}