#include <cstdio>
#include <vector>
#define NMAX 10023
#define DIM 10000
using namespace std;
char buff[DIM];
int poz=0;
void citeste(int &numar)
{
     numar = 0;
     while (buff[poz] < '0' || buff[poz] > '9')
          if (++poz == DIM)
               fread(buff,1,DIM,stdin),poz=0;
     while ('0'<=buff[poz] && buff[poz]<='9')
     {
          numar = numar*10 + buff[poz] - '0';
          if (++poz == DIM)
               fread(buff,1,DIM,stdin),poz=0;
     }
}
vector<int>adj[NMAX];
int l[NMAX],r[NMAX],st[NMAX];
bool v[NMAX];
int n,m,e;
int pairup(const int &nod)
{
    if(v[nod]) return 0;
    v[nod]=1;
    int mar=adj[nod].size();
    for(int i=0;i<mar;i++)
    {
        if(r[adj[nod][i]]==0)
        {
            l[nod]=adj[nod][i];
            r[adj[nod][i]]=nod;
            return 1;
        }
    }
    for(int i=0;i<mar;i++)
    {
        if(pairup(r[adj[nod][i]]))
        {
    //        printf("aaa\n");
            l[nod]=adj[nod][i];
            r[adj[nod][i]]=nod;
            return 1;
        }
    }
    return 0;
}
inline void show_sol()
{
    for(int i=1;i<=n;i++)
    {
        if(l[i]==0) continue;
        printf("%d %d\n",i,l[i]);
    }
}
int main()
{
    freopen ("cuplaj.in","r",stdin);
    freopen ("cuplaj.out","w",stdout);
    citeste(n),citeste(m),citeste(e);
    int x1,x2;
    for(int i=1;i<=e;i++)
    {
        citeste(x1),citeste(x2);
        adj[x1].push_back(x2);
    }
    for(int c=1;c!=0;)
    {
        c=0;
        for(int i=1;i<=n;i++)
        {
            if(l[i]==0) c|=pairup(i);
        }
        for(int i=1;i<=n;i++) v[i]=0;
    }
    int cuplaj=0;
    for(int i=1;i<=n;i++)
    {
        if(l[i]!=0) cuplaj++;
    }
    printf("%d\n",cuplaj);
    show_sol();
}