#include <bits/stdc++.h>

using namespace std;

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

vector <int> G[50005];

int l[50005], r[50005], u[50005];

int pairup(int n)
{
    if(u[n])
    {
        return 0;
    }
    u[n] = 1;
    for(vector <int>::iterator i = (G[n]).begin(); i != (G[n]).end(); ++ i)
    {
        if(!r[*i])
        {
            l[n] = *i;
            r[*i] = n;
            return 1;
        }
    }
    for(vector <int>::iterator i = (G[n]).begin(); i != (G[n]).end(); ++ i)
    {
        if(pairup(r[*i]))
        {
            l[n] = *i;
            r[*i] = n;
            return 1;
        }
    }
    return 0;
}

int main()
{
    int n, m, k;
    fin>>n>>m>>k;
    while(k)
    {
        int x, y;
        fin>>x>>y;
        G[x].push_back(y);
        k--;
    }
    int change = 1;
    while(change == 1)
    {
        change = 0;
        //memset(u, 0, sizeof(u));
        for(int i = 1; i <= n; i++)
        {
            u[i]=0;
        }
        for(int i = 1; i <= n; i++)
        {
            if(!l[i])
            {
                change |= pairup(i);
            }
        }
    }
    int cuplaj = 0;
    for(int i = 1; i <= n; i++)
    {
        if(l[i] > 0)
        {
            cuplaj++;
        }
    }
    fout<<cuplaj;
    fout<<'\n';
    for(int i = 1; i <= n; i++)
    {
        if(l[i] > 0)
        {
            fout<<i<<" "<<l[i]<<'\n';
        }
    }

    return 0;
}