#include <fstream>
#include <vector>

using namespace std;
ifstream f("cuplaj.in");
ofstream g("cuplaj.out");
vector <int> v[10001];
int n,m,e,l[10001],r[10001],sel[10001],nr;
int cupleaza(int nod)
{
    sel[nod]=1;
    for(auto it:v[nod])
        if(!r[it])
        {
            l[nod]=it;
            r[it]=nod;
            return 1;
        }
    for(auto it:v[nod])
        if(!sel[r[it]]&&cupleaza(r[it]))
        {
            r[it]=nod;
            l[nod]=it;
            return 1;
        }
    return 0;
}
int main()
{   int i,x,y,done=1;
    f>>n>>m>>e;
    for(i=1;i<=e;i++)
    {
        f>>x>>y;
        v[x].push_back(y);
    }
    while (done)
    {
        done=0;
        for(i=1;i<=n;i++) sel[i]=0;
        for(i=1;i<=n;i++)
            if(!l[i]&&!sel[i])
                done|=cupleaza(i);
    }
    for(i=1;i<=n;i++)
        if(l[i]) nr++;
    g<<nr<<'\n';
    for(i=1;i<=n;i++)
        if(l[i])
            g<<i<<" "<<l[i]<<'\n';
    return 0;
}