#include <iostream>
#include <fstream>
#include <vector>
#include <cstring>
using namespace std;

const int N = 10010;
const int M = 100010;

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

int n,m,e,co;
vector<int> v[N];
int pl[N],pr[N],mark[N];

int pair_up(int x)
{
    if ( pr[x] == 0 )
        return 1;
    int y = pr[x];
    if ( mark[y] == 1 )
        return 0;
    mark[y] = 1;
    for (int j=0;j<int(v[y].size());++j)
        if ( pair_up(v[y][j]) )
        {
            pl[y] = v[y][j];
            pr[v[y][j]] = y;
            return 1;
        }
    return 0;
}

int main()
{
    F>>n>>m>>e;
    for (int i=1,x,y;i<=e;++i)
    {
        F>>x>>y;
        v[x].push_back(y);
    }
    for (int i=1;i<=n;++i)
    {
        memset(mark,0,sizeof(mark));
        for (int j=0;j<int(v[i].size());++j)
            if ( pair_up(v[i][j]) )
            {
                pl[i] = v[i][j];
                pr[v[i][j]] = i;
                ++co;
                break;
            }
    }
    G<<co<<'\n';
    for (int i=1;i<=n;++i)
        if ( pl[i] != 0 )
            G<<i<<' '<<pl[i]<<'\n';
}