#include<stdio.h>
#include<algorithm>
#include<vector>
using namespace std;
int N,M,K;
int v[25000],x,p=0;
char car;
vector <int> g[25000];
int l[25000],r[25000],u[25000],was[25000],S;
int cupj(int q)
{
    if(was[q])
        return 0;
    was[q]=1;
    for(auto x : g[q])
    {
        if(!r[x])
        {
 
            l[q]=x;
            r[x]=q;
            return 1;
        }
    }
    for(auto x: g[q])
    {
        if(cupj(r[x])) {
            l[q]=x;
            r[x]=q;
            return 1;
        }
    }
    return 0;
}
int L,R,y;
 
int main()
{
freopen("cuplaj.in","r",stdin);
freopen("cuplaj.out","w",stdout);
    scanf("%d%d%d\n",&L,&R,&M);
    for(int i=1;i<=M;++i)
    {
        scanf("%d%d",&x,&y);
            g[x].push_back(y);
    }
 
   int ok=1;
   while(ok)
   {
    ok=0;
    for(int i=0;i<=L;++i)
        was[i]=0;
    for(int i=1;i<=L;++i)
        if(!l[i])
        {
            ok|= cupj(i);
        }
   }
   for(int i=1;i<=L;++i)
    if(l[i]>0)
        ++S;
    printf("%d\n",S);
    for(int i=1;i<=M;++i)
        if(l[i]>0)
        {
            printf("%d %d\n",i,l[i]);
        }
 
 
}