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

#define Nmax 10005

using namespace std;
int S,D,M;
int L[Nmax],R[Nmax];
vector<int> G[Nmax];
bitset<Nmax> used;

void Read()
{
    scanf("%d%d%d",&S,&D,&M);
    int a,b;
    for(int i = 1; i <= M; ++i){
        scanf("%d%d",&a,&b);
        G[a].push_back(b);
    }
}

int cuplaj(int k)
{
    if(used[k])
        return 0;
    used[k] = 1;
    for(vector<int>::iterator it = G[k].begin(); it != G[k].end(); ++it)
        if(!R[*it])
        {
            L[k] = *it;
            R[*it] = k;
            return 1;
        }

    for(vector<int>::iterator it = G[k].begin(); it != G[k].end(); ++it)
        if(cuplaj(R[*it]))
        {
            L[k] = *it;
            R[*it] = k;
            return 1;
        }
    return 0;
}

void Solve()
{
    int ok = 1,nrm = 0;
    while(ok){
        ok = 0;
        for(int i = 1; i <= S; ++i)
            if(!L[i] && cuplaj(i))
            {
                ok = 1;
                ++nrm;
            }
        used = 0;
    }
    printf("%d\n",nrm);
}


void Print()
{
    for(int i = 1; i <= S; ++i)
        if(L[i])
            printf("%d %d\n",i, L[i]);

}

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

    Read();
    Solve();
    Print();

    return 0;
}