#include<fstream>
#include<vector>
#include<algorithm>
using namespace std;
ifstream f("cuplaj.in");
ofstream o("cuplaj.out");

vector <int> a[10010];
int r[10010],l[10010],m,n,k,viz[100010];
int cupleaza(int nod){
	if(viz[nod]==1)return 0;
	viz[nod]=1;
	for(int i=0;i<a[nod].size();i++)
	 if(r[a[nod][i]]==0){
	 	r[a[nod][i]] = nod;
	 	l[nod] = a[nod][i];
	 	return 1;
	 }
	 
	 for(int i=0;i<a[nod].size();i++)
	 if(cupleaza(r[a[nod][i]])){
	 	r[a[nod][i]] = nod;
	 	l[nod] = a[nod][i];
	 	return 1;
	 }
	 return 0;
}

int main(){
	f>>n>>m>>k;
	int y,x;
	for(int i=1;i<=k;i++){
		f>>x>>y;
		a[x].push_back(y);
	}
	int ok=1;
	while(ok){
		ok=0;
		for(int i=1;i<=n;i++)viz[i]=0;
		for(int i=1;i<=n;i++)
		 if(viz[i]==0 && l[i]==0)
		   ok = ok||cupleaza(i);
	}
	int nr=0;
	for(int i=1;i<=n;i++)
	 if(l[i]!=0)nr++;
	 o<<nr<<"\n";
	 	for(int i=1;i<=n;i++)
	 if(l[i]!=0)o<<i<<" "<<l[i]<<"\n";
}