#include <cstring>
#include <cstdio>
#include <vector>

#define NMAX 10005

using namespace std;

vector <vector <int>> v;

int a , b , m , node1 , node2 , c;
int r[NMAX] , l[NMAX];

bool viz[NMAX];
bool pair_up(int node);

int main() {
    freopen("cuplaj.in" , "r" , stdin);
    freopen("cuplaj.out" , "w" , stdout);

    scanf("%d %d %d" , &a , &b , &m);

    v.resize(a + 5);

    for(int i = 1 ; i <= m ; ++i) {
        scanf("%d %d" , &node1 , &node2);
        v[node1].push_back(node2);
    }

    bool flag = true;
    while(flag) {
        flag = false;
        memset(viz , 0 , sizeof(viz));

        for(int i = 1 ; i <= a ; ++i) {
            if(l[i] == 0 && pair_up(i)) {
                ++c;
                flag = true;
            }
        }
    }

    printf("%d\n" , c);

    for(int i = 1 ; i <= a ; ++i) {
        if(l[i] != 0)
            printf("%d %d\n" , i , l[i]);
    }
    return 0;
}

bool pair_up(int node) {
    if(viz[node]) {
        return 0;
    }

    viz[node] = 1;
    for(vector <int> :: iterator it = v[node].begin() ; it != v[node].end() ; ++it) {
        int p = *it;
        if(r[p] == 0 || pair_up(r[p])) {
            l[node] = *it;
            r[*it] = node;
            return 1;
        }
    }

    return 0;
}