#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define N 10001

FILE *f=fopen("cuplaj.in","r");
FILE *out=fopen("cuplaj.out","w");



int *g[N];
int s[N],d[N],v[N],n,m,cnt;

int pair(int o){

	if(v[o]==1) return 0;

	v[o]=1;
	int x;

	for(x=1;x<=g[o][0];x++){
		if(!d[g[o][x]]){
			s[o]=g[o][x];
			d[g[o][x]]=o;
			return 1;
		}
	}

	for(x=1;x<=g[o][0];x++) {
		if(pair(d[g[o][x]])){
			s[o]=g[o][x];
			d[g[o][x]]=o;
			return 1;
		}
	}
	return 0;
}

void date(){
	int x,y,i;
	fscanf(f,"%d%d%d",&n,&m,&cnt);

	for(i=1;i<=n;i++){ g[i]=(int*)realloc(g[i],sizeof(int));g[i][0]=0;}

	for(; cnt-- ; ){

		fscanf(f,"%d%d",&x,&y);

		g[x][0]++;
		g[x]=(int*)realloc(g[x],(g[x][0]+1)*sizeof(int));
                g[x][g[x][0]]=y;
	}
}




int main(){

	date();

	int stare;int i,nr=0;

	for(stare=1; stare ; ){
		memset(v,0,sizeof(v));

		stare=0;
		for(i=1;i<=n;i++)if(!s[i]) stare |= pair(i);
	}

	for(i=1;i<=n;i++) if(s[i]>0) nr++;
	fprintf(out,"%d\n",nr);
	for(i=1;i<=n;i++)  if(s[i]>0) fprintf(out,"%d %d\n",i,s[i]);

	return 0;
}