#include <iostream>
#include <fstream>
#include <vector>
#include <cstring>
using namespace std;
ifstream f("cuplaj.in");
ofstream g("cuplaj.out");
 vector <int> v[20005];
 int l[20005],r[20005],use[20005];

 int DFS(int x)
 { int i;
   if (use[x]) return 0;
     use[x]=1;

    for(i=0;i<v[x].size();i++)
     if (!r[v[x][i]])
     { l[x]=v[x][i];
       r[v[x][i]]=x;
       return 1;
     }

   for(i=0;i<v[x].size();i++)
     if (DFS(r[v[x][i]]))
     { l[x]=v[x][i];
       r[v[x][i]]=x;
       return 1;
     }

   return 0;
 }

int main()
{ int i,x,y,n1,n2,e,ok,sol=0;

    f>>n1>>n2>>e;
    for(i=1;i<=e;i++)
    { f>>x>>y;
       v[x].push_back(n1+y);
    }
     ok=1;
    while(ok)
    { ok=0;
      memset(use,0,sizeof(use));

      for(i=1;i<=n1;i++)
       if (!l[i] && DFS(i)) {ok=1; sol++;}
    }

    g<<sol<<"\n";
    for(i=1;i<=n1;i++)
     if (l[i]) g<<i<<" "<<l[i]-n1<<"\n";
    return 0;
}