#include<cstdio>
#include<vector>
#include<bitset>

using namespace std;

const int NMAX = 10000+5;
const int MMAX = 10000+5;

void Read(),Solve(),Print();

int N,M,E,Solution;
int Match_A[NMAX];
int Match_B[MMAX];
vector<int> A[NMAX];
bitset<NMAX> Viz;

int Pair_up(int nod)
{
    if(Viz[nod]) return 0;

    vector<int>::iterator it;

    Viz[nod]=1;

    for(it=A[nod].begin(); it!=A[nod].end(); it++)
        if(!Match_B[*it] || Pair_up(Match_B[*it]))
        {
            Match_A[nod]=*it;
            Match_B[*it]=nod;
            return 1;
        }

    return 0;
}

int main()
{
    Read();
    Solve();
    Print();

    return 0;
}

void Read()
{
    int x,y;

    freopen("cuplaj.in","r",stdin);
    freopen("cuplaj.out","w",stdout);

    scanf("%d%d%d",&N,&M,&E);

    for(; E; --E)
    {
        scanf("%d%d",&x,&y);
        A[x].push_back(y);
    }
}

void Solve()
{
    int i,ok;

    for(ok=1; ok; )
    {
        ok=0;
        Viz=0;
        for(i=1; i<=N; i++)
            if(!Match_A[i]) ok|=Pair_up(i);
    }
}

void Print()
{
    int i;

    for(i=1; i<=N; i++)
        if(Match_A[i]) Solution++;

    printf("%d\n",Solution);

    for(i=1; i<=N; i++)
        if(Match_A[i]) printf("%d %d\n",i,Match_A[i]);
}