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

int i,j,n,m,r[200010],l[200010],x,y,e,rez=0;
vector<int> b[200010];
int cupleaza(int x)
{
	int i,ok,j,xx;
	for(i=0;i<b[x].size();++i)
		if(!r[b[x][i]])
		{
			l[x]=b[x][i];
			r[b[x][i]]=x;
			return 1;
		}
		ok=0;
		for(i=0;i<b[x].size()&&!ok;++i)
		{
			xx=r[b[x][i]];
			for(j=0;j<b[xx].size()&&!ok;++j)
				if(!r[b[xx][j]])
				{
					l[xx]=b[xx][j];
					r[b[xx][j]]=xx;
					ok=1;
				}
				if(ok)
				{
					l[x]=b[x][i];
					r[b[x][i]]=x;
					return 1;
				}
		}
		return 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+n);
		b[y+n].push_back(x);
	}
	for(i=1;i<=n;++i)
		if(!l[i])
			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]-n);
	return 0;
}