#include<fstream>
#include<vector>
#include<bitset>
using namespace std;
#define NMAX 10005
ifstream fin("cuplaj.in");
ofstream fout("cuplaj.out");
vector <int> v[NMAX];
bitset <NMAX> viz;
int n,m,k,x,y,ok,sol,L[NMAX],R[NMAX];
int cupleaza(int s)
{
    int i,z;
    viz[s]=1;
    for (i=0;i<v[s].size();++i)
    {
        z=v[s][i];
        if (R[z]==0)
        {
            L[s]=z, R[z]=s;
            return 1;
        }
    }
    for (i=0;i<v[s].size();++i)
    {
        z=v[s][i];
        if (viz[R[z]]==0 && cupleaza(R[z]))
        {
            L[s]=z, R[z]=s;
            return 1;
        }
    }
    return 0;
}
int main()
{
    int i;
    fin>>n>>m>>k;
    for (i=0;i<k;++i)
    {
        fin>>x>>y;
        v[x].push_back(y);
    }
    do
    {
        for (i=1;i<=n;++i)
            viz[i]=0;
        ok=0;
        for (i=1;i<=n;++i)
            if (L[i]==0 && cupleaza(i))
                ok=1;
    } while (ok);
    for (i=1;i<=n;++i)
        if (L[i])
            ++sol;
    fout<<sol<<"\n";
    for (i=1;i<=n;++i)
        if (L[i])
            fout<<i<<" "<<L[i]<<"\n";
    return 0;
}