#include <fstream>
#include <vector>
#include <cstring>
#define nmax 10005
using namespace std;
vector <int> a[nmax];
int l[nmax],r[nmax];
bool viz[nmax];
bool cuplare(int x)
{
    if (viz[x]) return 0;
    viz[x]=1;
    int i,y;
    for (i=0;i<a[x].size();i++)
    {
        y=a[x][i];
        if (!r[y])
        {
            l[x]=y;
            r[y]=x;
            return 1;
        }
    }
    for (i=0;i<a[x].size();i++)
    {
        y=a[x][i];
        if (cuplare(r[y]))
        {
            l[x]=y;
            r[y]=x;
            return 1;
        }
    }
    return 0;
}
int main()
{
    ifstream f("cuplaj.in");
    ofstream g("cuplaj.out");
    int i,j,x,n,m,e,y,cuplaj=0;
    f>>n>>m>>e;
    for (i=1;i<=e;i++)
    {
        f>>x>>y;
        a[x].push_back(y);
    }
    for (i=1;i<=n;i++)
    {
        //fiecare nod din L
        if (!l[i])
        {
            if (!cuplare(i))
            {
                memset(viz,0,sizeof(viz));
                cuplaj+=(cuplare(i));
            }
            else cuplaj++;
        }
    }
    g<<cuplaj<<'\n';
    for (i=1;i<=n;i++)
    {
        if (l[i]>0)
        {
            g<<i<<' '<<l[i]<<'\n';
        }
    }
    f.close();
    g.close();
    return 0;
}