#include <bits/stdc++.h>
using namespace std;

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

int n1, n2, m;
vector<int> graf[10001];

int l[10001], r[10001];   // l[j] = partenerul din stanga al lui j
                          // r[i] = partenerul din dreapta al lui i

int distanta[10001];

bool bfs()
{
    queue<int> q;

    for (int i=1; i<=n1; i++)
    {
        if (r[i]==0)
        {
            distanta[i]=0;
            q.push(i);
        }
        else
        {
            distanta[i]=-1;
        }
    }
    bool exista_drum_augmentare=false;
    while (!q.empty())
    {
        int nod=q.front();
        q.pop();
        for (auto u : graf[nod])
        {
            if (l[u]==0)
            {
                exista_drum_augmentare=true;
            }
            else if (distanta[l[u]]==-1)
            {
                distanta[l[u]]=distanta[nod]+1;
                q.push(l[u]);
            }
        }
    }
    return exista_drum_augmentare;
}

bool dfs(int nod)
{
    for (auto u : graf[nod])
    {
        if (l[u]==0 || (distanta[l[u]]==distanta[nod]+1 && dfs(l[u])))
        {
            l[u]=nod;
            r[nod]=u;
            return true;
        }
    }
    distanta[nod]=-1;
    return false;
}

int main()
{
    fin>>n1>>n2>>m;
    for (int i=1; i<=m; i++)
    {
        int a, b;
        fin>>a>>b;
        graf[a].push_back(b);
    }
    int rez=0;
    while (bfs())
    {
        for (int i=1; i<= n1; i++)
        {
            if (r[i]==0 && dfs(i))
            {
                rez++;
            }
        }
    }

    fout<<rez<<'\n';
    for (int i=1; i<=n1; i++)
    {
        if (r[i]!=0)
        {
            fout<<i<<" "<<r[i]<<'\n';
        }
    }

    return 0;
}