#include <iostream>
#include<fstream>
using namespace std;

ifstream f("cuplaj.in");
ofstream g("cuplaj.out");
int na,m,e,n;
int c[20005],viz[20005];
struct nod
{
    int inf;
    nod *succ;
}*v[20005];
int vecin(int x)
{

    nod *p;
    p=v[x];
    while(p)
      if(c[p->inf]==-1)return p->inf;
      else p=p->succ;

    return -1;
}
void construire()
{
    int i,k;
    for(i=1;i<=na;i++)
       {
          k=vecin(i);
          if(k!=-1)
          {c[i]=k;
          c[k]=i;break;}
       }
}
int dfs(int i)
{
    int j,k;
    viz[i]=1;
    nod *p;
    p=v[i];
    while(p)
       {
           k=p->inf;
           if(viz[k]||c[i]==k) goto hell;
           if(c[k]==-1)
           {
               viz[k]=1;
               c[k]=i;
               c[i]=k;
               return 1;
           }
           else
              {
                  viz[k]=1;
                  if(dfs(c[k]))
                     {
                         c[i]=k;
                         c[k]=i;
                         return 1;
                     }
              }
              hell:
              p=p->succ;
       }
    return 0;
}
void adauga(int x,int y)
{
    nod *p,*q;
    p=new nod;
    p->inf=y;
    p->succ=NULL;
    q=v[x];
    if(q==NULL)
       v[x]=p;
    else
     {

         while(q->succ)q=q->succ;
         q->succ=p;
     }
}
int main()
{
    int x,y,i,j,ok=1,nr=0;
    nod *p;
    f>>na>>m>>e;
    n=na+m;
    for(i=1;i<=n;i++)c[i]=-1;
    for(i=1;i<=e;i++)
      {
          f>>x>>y;
          y=y+na;

          adauga(x,y);


          adauga(y,x);
      }
      construire();
      //cerr<<1;
      while(ok)
      {
          ok=0;
          for(i=1;i<=n;i++)viz[i]=0;
          for(i=1;i<=na;i++)
             if(viz[i]==0&&c[i]==-1)
                 if(dfs(i))ok=1;
      }
     // for(i=1;i<=n;i++)cout<<c[i]<<" ";
      /*for(i=1;i<=n;i++)
         {for(j=0;j<l[i];j++)
            cout<<v[i][j]<<" ";
        cout<<"\n";}*/

    for(i=1;i<=na;i++)if(c[i]!=-1)nr++;
    g<<nr<<"\n";
    for(i=1;i<=na;i++)
       if(c[i]!=-1)
          g<<i<<" "<<c[i]-na<<"\n";
    return 0;
}