#include <bits/stdc++.h>

using namespace std;
ifstream f("cuplaj.in");
ofstream g("cuplaj.out");
vector <int> v[10005];
int dr[10005],st[10005],i,j,n,m,nrm,x,y,ok,sum,sel[10005];
bool cuplaj (int x)
{
    int i;
    sel[x]=1;
    for (i=0;i<v[x].size();i++)
    {
        if (dr[v[x][i]]==0)
        {
            st[x]=v[x][i];
            dr[v[x][i]]=x;
            return 1;
        }
    }
    for (i=0;i<v[x].size();i++)
    {
        if (sel[dr[v[x][i]]]==0&&cuplaj(dr[v[x][i]])==1)
        {
            st[x]=v[x][i];
            dr[v[x][i]]=x;
            return 1;
        }
    }
    return 0;
}
int main()
{
    f>>n>>m>>nrm;
    for (i=1;i<=nrm;i++)
    {
        f>>x>>y;
        v[x].push_back(y);
    }
    ok=1;
    while (ok==1)
    {
        for (i=1;i<=n;i++)
        {
            sel[i]=0;
        }
        ok=0;
        for (i=1;i<=n;i++)
        {
            if (st[i]==0&&sel[i]==0)
            {
                ok|=cuplaj(i);
            }
        }
    }
    for (i=1;i<=n;i++)
    {
        if (st[i]!=0)
        {
            sum++;
        }
    }
    g<<sum<<'\n';
    for (i=1;i<=n;i++)
    {
        if (st[i]!=0)
        {
            g<<i<<" "<<st[i]<<'\n';
        }
    }
    return 0;
}