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

#define Nmax 10005

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

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

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

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

    read();
    int ok = 1;
    int nre = 0;
    while(ok)
    {
        ok = 0;
        used = 0;
        for(int i = 1; i <= K; ++i)
            if(!L[i] && cuplaj(i))
            {
                ++nre;
                ok = 1;
            }
    }

    printf("%d\n",nre);
    for(int i = 1; i <= K; ++i)
        if(L[i])
            printf("%d %d\n",i,L[i]);


    return 0;
}