#include<bits/stdc++.h>
#define inf INT_MAX
using namespace std;
ifstream f("cuplaj.in");
ofstream g("cuplaj.out");
int n, m, e, a, b;
vector<int> v[20001];
queue<int> q;
int lv[20001];
int st[20001], dr[20001];
bool bfs()
{
    for(int i = 1 ; i <= n ; i++)
        if(!dr[i])
            q.push(i), lv[i] = 0;
        else
            lv[i] = inf;///nod cuplat [i, dr[i]]
    lv[0] = inf;///nodurile necuplate sunt cuplate cu 0
    while(!q.empty())
    {
        int node = q.front();
        q.pop();
        if(lv[node] < lv[0]) ///daca il cuplez pe 0 cu cineva => am gasit cuplaj din lant de lungime minimia
        {
            for(auto next : v[node])
            {
                if(lv[st[next]] == inf) ///next e cuplat cu st[next]
                {
                    lv[st[next]] = 1 + lv[node];///[node , next]; [next , st[next]]
                    q.push(st[next]);
                }
            }
        }
    }
    return lv[0] != inf;///am gasit un lant
}
bool dfs(int node)
{
    if(node != 0)
    {
        for(auto next : v[node])
            if(1 + lv[node] == lv[st[next]] && dfs(st[next]))
            {
                ///lv[node] + 1 == lv[st[next]] => [node , next] necuplat , [next , st[next]] cuplat
                ///daca dfs(st[next]) => [node , next] cuplat
                st[next] = node;
                dr[node] = next;
                return true;
            }
        lv[node] = inf;///nu am gasit cuplaj
        return false;
    }
    return true;
}
int maxmatch()
{
    int ans = 0;
    while(bfs())
    {
        for(int i = 1 ; i <= n ; i++)
            if(!dr[i] && dfs(i))
                ans++;
    }
    return ans;
}
int main()
{
    f >> n >> m >> e;
    fill(st, st + 20001, 0);
    fill(dr, dr + 20001, 0);
    for(int i = 1 ; i <= e ; i++)
    {
        f >> a >> b;
        v[a].push_back(b);
    }
    g << maxmatch() << '\n';
    for(int i = 1 ; i <= m ; i++)
        if(st[i])
            g << st[i] << ' ' << i << '\n';
    return 0;
}