#include<stdio.h>
#include<algorithm>
#include<vector>
using namespace std;
vector <int> nr[10010];
int viz[10010];
int st[10010],dr[10010];
bool cupleaza(int x){
	if(viz[x])
		return false;
	viz[x]=1;
	for(int i=0;i<nr[x].size();++i){
		if(!dr[nr[x][i]]){
			st[x]=nr[x][i];
			dr[nr[x][i]]=x;
			return true;
		}
	}
	for(int i=0;i<nr[x].size();++i){
		if(cupleaza(dr[nr[x][i]])){
			st[x]=nr[x][i];
			dr[nr[x][i]]=x;
			return true;
		}
	}
	return false;
}
int main(){
	freopen("cuplaj.in","r",stdin);
	freopen("cuplaj.out","w",stdout);
	int n,e,m,i,x,y;
	scanf("%d%d%d",&n,&m,&e);
	for(i=0;i<e;++i){
		scanf("%d%d",&x,&y);
		nr[x].push_back(y);
	}
	int cuplaj=0;
	for(i=1;i<=n;++i){
		if(!st[i]){
			if(!cupleaza(i)){
				memset(viz,0,sizeof(viz));
				cuplaj+=cupleaza(i);
			}
			else
				++cuplaj;
		}
	}
	printf("%d\n",cuplaj);
	for(i=1;i<=n;++i){
		if(st[i]>0)
			printf("%d %d\n",i,st[i]);
	}
	fclose(stdin);
	fclose(stdout);
	return 0;
}