#include <bits/stdc++.h>
#define NMAX 10009
using namespace std;
ifstream fin("cuplaj.in");
ofstream fout("cuplaj.out");
int ns,nd,m;

vector <int>g[NMAX];
bool ok;
int uz[NMAX],nr;
int st[NMAX],dr[NMAX];
void citire();
bool cup(int node);
int main()
{
citire();
ok=1;
while(ok)
{
 ok=0;

 memset(uz,0,sizeof(uz));
 for(int i=1;i<=ns;i++)
    if(!st[i] && !uz[i])
       if(cup(i))
         ok=1;

}
memset(uz,0,sizeof(uz));
for(int i=1;i<=ns;i++)
    if(st[i] )
        {nr++;/*fout<<i<<" "<<st[i]<<'\n';*/}
fout<<nr<<'\n';
for(int i=1;i<=ns;i++)
    if(st[i] )
        {fout<<i<<" "<<st[i]<<'\n';}

    return 0;
}
void citire()
{int i,x,y;
  fin>>ns>>nd>>m;
 for(i=1;i<=m;i++)
    {
     fin>>x>>y;
     g[x].push_back(y);
        //g[x].push_back(x);
    }
}
bool cup(int node)
{
 int i,vec;
 if(uz[node])
    return 0;
 uz[node]=1;
 for(i=0;i<g[node].size();i++)
    {
     vec=g[node][i];
     if(!dr[vec]) ///pun muchie
        {
          st[node]=vec;///cuplez
          dr[vec]=node;
          return 1;
        }

    }
 for(i=0;i<g[node].size();i++)
    {
     vec=g[node][i];
     if(cup(dr[vec]) )
        {
         st[node]=vec;
         dr[vec]=node;
         return 1;
        }
    }
   return 0;

}