#include <cstdio>
#include <vector>

using namespace std;

#define file_in "cuplaj.in"
#define file_out "cuplaj.out"

#define nmax 101000

int n,m,e;
int r[nmax];
int l[nmax];
int viz[nmax];
vector<int> G[nmax];
int ok,nr,a,b,i;

int cupleaza(int nod){
	
	if (viz[nod])
		return 0;
	
	viz[nod]=1;
	
	vector<int> :: iterator it;
	
	for (it=G[nod].begin();it!=G[nod].end();++it)
		 if (!r[*it]){
			 l[nod]=*it;
			 r[*it]=nod;
			 return 1;
		 }
	for (it=G[nod].begin();it!=G[nod].end();++it)
		 if (cupleaza(r[*it])){
			 l[nod]=*it;
			 r[*it]=nod;
			 return 1;
		 }	 
	return 0;

}
		 

int main(){
	
	freopen(file_in,"r",stdin);
	freopen(file_out,"w",stdout);
	
	scanf("%d %d %d", &n, &m,&e);
	for (i=1;i<=e;++i){
		
		scanf("%d %d",&a, &b);
		G[a].push_back(b);
	}
	
	ok=1;
	
	while(ok){
		
		ok=0;
		memset(viz,0,sizeof(viz));
		for (i=1;i<=n;++i)
			 if (!l[i]){
				if (cupleaza(i))
				 ok=1;
			 }
	}
	
	nr=0;
	for (i=1;i<=n;++i)
		 if (l[i])
			 nr++;
		 
	printf("%d\n", nr);
	for (i=1;i<=n;++i)
		 if (l[i])
			 printf("%d %d\n", i, l[i]);
		 
	return 0;

}