#include<fstream>
#include<vector>
#include<cstring>
#define pb push_back
#define Nmax 10009

using namespace std;

ifstream in("cuplaj.in");
ofstream out("cuplaj.out");

int nod2,x,y,N,N2,M,i,ok,nr,st[Nmax],dr[Nmax],OK[Nmax];
vector<int> a[Nmax];

int cupleaza(int nod)
{
    vector<int>::iterator it;
    int nod2;

    OK[nod]=1;

    for (it=a[nod].begin();it!=a[nod].end();it++)
    {
        nod2=*it;
        if (!dr[nod2] || (!OK[dr[nod2]] && cupleaza(dr[nod2])))
        {
            st[nod]=nod2;
            dr[nod2]=nod;
            return 1;
        }
    }
    return 0;
}

int main()
{
    in>>N>>N2>>M;

    for (i=1;i<=M;i++)
    {
        in>>x>>y;
        a[x].pb(y);
    }

    ok=1;
    while (ok)
    {
        memset(OK,0,sizeof(OK));
        ok=0;
        for (i=1;i<=N;i++)
        {
            if (st[i]) continue;
            if (cupleaza(i))
            {
                ok=1;
                nr++;
            }
        }
    }
    out<<nr<<'\n';
    for (i=1;i<=N;i++)
        if (st[i]) out<<i<<' '<<st[i]<<'\n';
}