#include<fstream>
#include<vector>
#include <algorithm>
using namespace std;
int n,m,e,x,y,v[22000],l[11000],r[11000],sol;
vector<int> a[22000];
int cuplaj(int x)
{
    if(v[x])
        return 0;
    v[x]=1;
    int y=a[x].size(),i;
    for (i=0;i<y;i++)
            if(r[a[x][i]]==0)// se conecteaza cu cineva cu care nu a fost cuplat
            {
                l[x]=a[x][i];
                r[a[x][i]]=x;
                return 1;
            }
    for (i=0;i<y;i++)
        if(cuplaj(r[a[x][i]])==1) // incerc sa recuplez
        {
            l[x]=a[x][i];
            r[a[x][i]]=x;
            return 1;
        }
    return 0;
}
int main()
{
    fstream f,g;
    int i,ok=1;
    f.open("cuplaj.in",ios::in);
    g.open("cuplaj.out",ios::out);
    f>>n>>m>>e;
    for (i=1;i<=e;i++)
    {
        f>>x>>y;
        a[x].push_back(y);
    }
    while(ok)
    {
        ok=0;
        for (i=1;i<=n;i++)
            v[i]=0;
        for (i=1;i<=n;i++)
            if(l[i]==0)
                if(cuplaj(i)==1)
                    ok=1;
    }
    int nr=0;
    for(i=1;i<=n;++i)
        if(l[i])
            sol++;
    g<<sol<<"\n";
    for (i=1;i<=n;i++)
        if(l[i])
            g<<i<<" "<<l[i]<<'\n';
}