#include<stdio.h>
#include<vector>
#include<algorithm>
#define nmax 10001
using namespace std;
int pairup(int);
vector<int>g[nmax];
int l[nmax],r[nmax],u[nmax],n,m,nr;
int main(){
	freopen("cuplaj.in","r",stdin);
	freopen("cuplaj.out","w",stdout);
	scanf("%d %d %d",&n,&m,&nr);
	for(;nr!=0;nr--){
		int x,y;
		scanf("%d %d",&x,&y);
		g[x].push_back(y);
	}
	int c=1;
	while(c!=0){
		c=0;
		memset(u,0,sizeof(u));
		for(int i=1;i<=n;i++)
			if(!l[i])
				c|=pairup(i);
	}
	int c1=0;
	for(int i=1;i<=n;i++)
		c1=c1+(l[i]>0);
	printf("%d\n",c1);
	for(int i=1;i<=n;i++)
		if(l[i]>0)
			printf("%d %d\n",i,l[i]);
	return 0;
}
int pairup(int n){
	if(u[n]!=0)return 0;
	u[n]=1;
	for(vector <int>::iterator t =(g[n]).begin();t!=(g[n]).end();t++)
		if(!r[*t]){
			l[n]=*t;
			r[*t]=n;
			return 1;
		}
	for(vector <int>::iterator t =(g[n]).begin();t!=(g[n]).end();t++)
		if(pairup(r[*t])){
			l[n]=*t;
			r[*t]=n;
			return 1;
		}
		return 0;
}