#include <iostream>
#include <cstdio>
#include <vector>
#include <bitset>
#include <utility>
#include <algorithm>
 
#define NMAX 10005
#define pb push_back
 
using namespace std;
 
vector<int> G[NMAX];
int L[NMAX], R[NMAX];
bitset<NMAX> U;
int n, m, e;
 
bool pairup(int nod)
{
    if (U[nod]) return 0;
    U[nod] = 1;
 
    for (vector<int> ::iterator it = G[nod].begin(); it != G[nod].end(); ++it)
        if (!R[*it])
        {
            L[nod] = *it;
            R[*it] = nod;
            return 1;
        }
    for (vector<int> ::iterator it = G[nod].begin(); it != G[nod].end(); ++it)
        if (pairup(R[*it]))
        {
            L[nod] = *it;
            R[*it] = nod;
            return 1;
        }
    return 0;
}
int main()
{
    freopen("cuplaj.in", "rt", stdin);
    freopen("cuplaj.out", "w", stdout);
 
    int x, y;
 
    cin >> n >> m >> e;
    while (e--)
    {
        cin >> x >> y;
        G[x].push_back(y);
    }
 
    for (bool change = 1; change;)
    {
        change = 0;
        U.reset();
        for (int i = 1; i <= n; ++i)
            if (!L[i]) change |= pairup(i);
    }
 
    int dimCuplaj = 0;
    for (int i = 1; i <= n; ++i)
        dimCuplaj += (L[i] > 0);
    cout << dimCuplaj << '\n';
 
    for (int i = 1; i <= n; ++i)
        if (L[i]) cout << i << ' ' << L[i] << '\n';
    return 0;
}