#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(int i=0;i<g[q].size();++i)
    {
        if(!r[g[q][i]])
        {

            l[q]=g[q][i];
            r[g[q][i]]=q;
            return 1;
        }
    }
    for(int i=0;i<g[q].size();++i)
    {
        if(cupj(r[g[q][i]]))
        {
            l[q]=g[q][i];
            r[g[q][i]]=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);
    }

  /* for(int i=1;i<=M;++i)
   {
       for(int j=0;j<g[i].size();++j)
        printf("%d ",g[i][j]);
    printf("\n");
   }*/
   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]);
        }


}