#include<stdio.h>
#include<algorithm>
#include<vector>
using namespace std;
vector <int> nr[10010];
int viz[10010];
int st[10010],dr[10010];
int cupleaza(int x){
	if(viz[x])
		return false;
	viz[x]=1;
	for(vector<int>::iterator it=nr[x].begin();it!=nr[x].end();++it){
		if(!dr[*it]){
			st[x]=*it;
			dr[*it]=x;
			return true;
		}
	}
	for(vector<int>::iterator it=nr[x].begin();it!=nr[x].end();++it){
		if(cupleaza(dr[*it])){
			st[x]=*it;
			dr[*it]=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,mod;
	for(mod=1;mod;){
		mod=0;
		memset(viz,0,sizeof(viz));
		for(i=1;i<=n;++i){
			if(!st[i])
				mod|=cupleaza(i);
		}
	}
	for(i=1;i<=n;++i){
		if(st[i])
			++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;
}