#include <iostream>
#include <fstream>
#include <vector>

using namespace std;

const int NM = 100001;
const int INF = 1 << 30;
const int NIL = 0;

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

int m, n, e;
int perechi_st[NM], perechi_dr[NM], d[NM], q[NM];

vector <int> a[NM];//vecinii fiecarui varf din stanga

bool bfs()
{
    int st = 0, dr = -1, x, z;
    //initializare d
    for (int i = 1; i <= n; i++)
    {
        if (perechi_st[i] == NIL)
        {
            d[i] = 0;
            q[++dr] = i;
        }
        else
        {
            d[i] = INF;
        }
    }

    d[NIL] = INF;
    while (st <= dr)
    {
        x = q[st++];
        if (d[x] < d[NIL])
        {
            for (auto y: a[x])
            {
                z = perechi_dr[y];
                if (d[z] == INF)
                {
                    d[z] = 1 + d[x];
                    q[++dr] = z;
                }
            }
        }
    }
    return (d[NIL] != INF);
}

bool dfs(int x)
{
    if (x == NIL)
    {
        return true;
    }
    for (auto y: a[x])
    {
        int z = perechi_dr[y];
        if (d[z] == 1 + d[x])
        {
            if (dfs(z))
            {
                perechi_st[x] = y;
                perechi_dr[y] = x;
                return true;
            }
        }
    }
    return false;
}

int main()
{
    in >> n >> m >> e;
    for (int i = 0; i < e; i++)
    {
        int x, y;
        in >> x >> y;
        a[x].push_back(y);
    }
    in.close();

    for (int i = 1; i <= n; i++)
    {
        perechi_st[i] = NIL;
    }
    for (int i = 1; i <= m; i++)
    {
        perechi_dr[i] = NIL;
    }

    int cuplaj = 0;
    while (bfs())
    {
        for (int i = 1; i <= n; i++)
        {
            if (perechi_st[i] == NIL && dfs(i))
            {
                cuplaj++;
            }
        }
    }
    out << cuplaj << "\n";
    for (int i = 1; i <= n; i++)
    {
        if (perechi_st[i] != NIL)
        {
            out << i << " " << perechi_st[i] << "\n";
        }
    }
    out.close();
    return 0;
}