#include <bits/stdc++.h>
#define N 10005
#define M 500001
#define inf 20000

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

int n, m;
bool findMatchBipartite(bool bip_graph[N][N], int vertex, bool seen[], int match[])//if we find a job for the current vertex
{
    //a dfs based function that tries all possibilites to assign a job to the applicant
    //if a job isn't assigned->we assign it
    //if it is assigned yo x, we try to check recursively if x can have another job
    //to make sure that we don't assign multiple times the same job to a cnadidate--> seen
    for(int i = 1; i <= m; ++ i)//try every job
    {
        if(bip_graph[i][vertex] && !seen[i])
        {
            seen[i] =1;//to not repeat it
            //if it s not assigned or it is assigned to smb that can have another job
            if(match[i] == -1 || findMatchBipartite(bip_graph, match[i], seen, match))
            {
                match[i] = vertex;
                return true;
            }
        }

    }
    return false;
}
void maxBipartite()
{
    bool bip_graph[N][N];
    //lines with jobs and columns with candidates
    int e;
    fin >> e;
    for(int i = 1; i <= e; ++i)
    {
        int x, y;
        fin >> x >> y;
        bip_graph[y][x] = 1;

    }
    //n -- aplicants(left)
    //m -- jobs(right)
    int match[N];//the applicant for job i, match or -1
    memset(match, -1, sizeof(match));
    int sol = 0;
    for(int i = 1; i <= n; ++i)//for every aplicant
    {
        bool seen[N];
        memset(seen, 0, sizeof(seen));//not seen
        if(findMatchBipartite(bip_graph, i,seen, match))
            sol++;//found  job;
    }
    fout << sol <<"\n";
    for(int i = 1; i <= m; ++i)//for every job that has an applicant
        if(match[i] != -1)
            fout << match[i] << " " << i << "\n";
}

int main()
{
    fin >> n >> m;
    maxBipartite();


  return 0;
}