#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define N 10001
int l[N],r[N],u[N],n,m,e,c=1,i,j,a[10*N],b[10*N],w[N],*g[N];
int P(int n)
{
    if(u[n])
		return 0;
    u[n]=1;
    int i;
    for(i=0;i<w[n];i++)
		if(!r[g[n][i]]) {
        	l[n]=g[n][i],r[g[n][i]]=n;
        	return 1;
    	}
    for(i=0;i<w[n];i++)
		if(P(r[g[n][i]])) {
        	l[n]=g[n][i],r[g[n][i]]=n;
        	return 1;
    	}
    return 0;
}
int main()
{
    freopen("cuplaj.in","r",stdin),freopen("cuplaj.out","w",stdout),scanf("%d%d%d",&n,&m,&e);
    for(i=0;i<e;i++)
        scanf("%d%d",a+i,b+i),++w[a[i]];
    for(i=1;i<=n;w[i++]=0)
        g[i]=(int*)malloc(4*w[i]);
    for(i=0;i<e;i++)
        g[a[i]][w[a[i]]++]=b[i];
    while(c)
        for(c=0,memset(u,0,sizeof(u)),i=1;i<=n;++i)
			if(!l[i])
            	c|=P(i);
    for(j=0,i=1;i<=n;++i)
		j+=(l[i]>0);
    for(printf("%d\n",j),i=1;i<=n;++i)
		if(l[i]>0)
        	printf("%d %d\n",i,l[i]);
    return 0;
}