#include <bits/stdc++.h>
#define N 10000
using namespace std;
ifstream f("cuplaj.in");
ofstream g("culaj.out");

int n,m,k,i,C,R[N],L[N],x,y,T[N],O=-1;
vector<int> v[N];

int P(int n)
{
if (T[n]==i)return 0;
T[n]=i;
for (auto j:v[n])
if (!L[j]){
    L[j]=n,R[n]=j;
    return 1;
}for (auto j:v[n])
if (P(L[j])){
    L[j]=n,R[n]=j;
    return 1;
}
return 0;
}

int main()
{
f>>n>>m>>k;
for (i=1;i<=k;++i)
    f>>x>>y,v[x].push_back(y);
for(i=1;i<=n;++i)
    if (!R[i])C+=P(i);
g<<C<<'\n';
for (i=1;i<=n;++i)
    if (R[i])g<<i<<" "<<R[i]<<'\n';

    return 0;
}