#include<fstream>
#include<vector>
using namespace std;
	FILE *g=fopen("cuplaj.out","w");

int i,j,n,m,r[200010],l[200010],uz[200010],x,y,e,rez=0;
vector<int> b[200010];
inline int cupleaza(int x)
{
	if(uz[x])
		return 0;
	uz[x]=1;
	for(int i=0;i<b[x].size();++i)
		if(!r[b[x][i]])
		{
			l[x]=b[x][i];
			r[b[x][i]]=x;
			return 1;
		}
		for(int i=0;i<b[x].size();++i)
			if(cupleaza(r[b[x][i]]))
			{
					l[x]=b[x][i];
					r[b[x][i]]=x;
					return 1;
		   }
		return 0;
}
void init()
{
	for(int i=1;i<=n+m;++i)
		uz[i]=0;
}
int main()
{
	FILE *f=fopen("cuplaj.in","r");
	fscanf(f,"%d%d%d",&n,&m,&e);
	for(i=1;i<=e;++i)
	{
		fscanf(f,"%d%d",&x,&y);
		b[x].push_back(y);
		b[y+n].push_back(x);
	}
	for(i=1;i<=n;++i)
		if(!l[i])
			init(),cupleaza(i);
		for(i=1;i<=n;++i)
			if(l[i])
				++rez;
			fprintf(g,"%d\n",rez);
			for(i=1;i<=n;++i)
				if(l[i])
					fprintf(g,"%d %d\n",i,l[i]);
	return 0;
}