#include <bits/stdc++.h>

using namespace std;



const char iname[] = "cuplaj.in";

const char oname[] = "cuplaj.out";



#define MAXN  10005

#define FOR(i, a, b)  for (int i = (int)(a); i <= (int)(b); ++ i)

#define FORI(i, V)    for (vector <int>::iterator i = (V).begin(); i != (V).end(); ++ i)



vector <int> G[MAXN];



int l[MAXN], r[MAXN], u[MAXN];





int pairup(const int n)

{

    if (u[n])  return 0;

    u[n] = 1;

    FORI (i, G[n]) if (!r[*i]) {

        l[n] = *i;

        r[*i] = n;

        return 1;

    }

    FORI (i, G[n]) if (pairup(r[*i])) {

        l[n] = *i;

        r[*i] = n;

        return 1;

    }

    return 0;

}



int main(void)

{

    freopen(iname, "r", stdin);

    freopen(oname, "w", stdout);



    int n, m, cnt_edges;

    scanf("%d %d %d", &n, &m, &cnt_edges);



    for (; cnt_edges --; )

    {

        int x, y;

        scanf("%d %d", &x, &y);

        G[x].push_back(y);

    }

    for (int change = 1; change; )

    {

        change = 0;

        memset(u, 0, sizeof(u));

        FOR (i, 1, n) if (!l[i])

            change |= pairup(i);

    }

    int cuplaj = 0;

    FOR (i, 1, n)  cuplaj += (l[i] > 0);

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

    FOR (i, 1, n) if (l[i] > 0)

        printf("%d %d\n", i, l[i]);



    return 0;

}