#include <fstream>
#include <string>
#include <cstring>
#include <map>
#include <algorithm>
#include <stack>
#include <deque>
#include <vector>
#include <queue>
#include <bitset>
#define Nmax 100001
using namespace std;

const int oo = 1 << 28;
typedef vector < int > VI;

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

int a, b, m, n, st[Nmax], dr[Nmax], ans, x, y; 
bool F[Nmax];
VI V[Nmax];

bool cuplaj(int vertex){
    if(F[vertex] == 1)
        return 0;

    F[vertex] = 1;

    for(int new_vertex : V[vertex])
        if(dr[new_vertex] == 0){
            st[vertex] = new_vertex;
            dr[new_vertex] = vertex;

            return 1;
        }

    for(int new_vertex : V[vertex])
        if(cuplaj(dr[new_vertex])){
            st[vertex] = new_vertex;
            dr[new_vertex] = vertex;

            return 1;
        }
    return 0;
}

int main() {
    fin >> a >> b >> m;

    for(int i = 1; i <= m; ++i){
        fin >> x >> y;

        V[x].push_back(y);
    }

    int done = 0;

    while(!done){
        done = 1;

        for(int i = 1; i <= a; ++i)
            F[i] = 0;

        for(int i = 1; i <= a; ++i)
            if(st[i] == 0 && cuplaj(i)){
                ++ans;
                done = 0;
            }
    }

    fout << ans << "\n";

    for(int i = 1; i <= a; ++i)
        if(st[i])
            fout << i << " " << st[i] << "\n";

    return 0;
}