#include <bits/stdc++.h>
#define N 10000
using namespace std;
ifstream f("cuplaj.in");
ofstream g("cuplaj.out");
int n,m,k,i,C,R[N],L[N],x,y;
vector<int> v[N];
bitset<N> T;

int P(int n)
{
if (T[n])return 0;T[n]=1;
for (auto j:v[n])if (!L[j])
     return L[j]=n,R[n]=j;
for (auto j:v[n])if (P(L[j]))
    return L[j]=n,R[n]=j;
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]&&P(i))++C,T=0;
g<<C<<'\n';
for (i=1;i<=n;++i)
    if (R[i])g<<i<<" "<<R[i]<<'\n';

    return 0;
}