#include <bits/stdc++.h>
#define Nmax 20005
using namespace std;

ifstream f("cuplaj.in");
ofstream g("cuplaj.out");

int N, M, E, ans;
vector<int> G[Nmax];
int le[Nmax], ri[Nmax];
bitset<Nmax> vis;
bool match(int x) {
    if (vis[x]) return 0;
    vis[x] = 1;

    for (auto y: G[x])
    if (!le[y]) {
          ri[x] = y;
          le[y] = x;
          return 1;
     }
    for (auto y: G[x])
    if (match(le[y])) {
        ri[x] = y;
        le[y] = x;
        return 1;
    }
      return 0;
}
int main()
{
    f >> N >> M >> E;
    for (int i = 1; i <= E; ++i) {
        int x, y;
        f >> x >> y;
        G[x].push_back(y + N);
    }

    for (int i = 1; i <= N; ++i) {
        vis.reset();
        if (!ri[i] && match(i)) ++ans;
    }

    g << ans << '\n';
    for (int i = 1; i <= N; ++i)
        if (ri[i]) g << i << " " << ri[i] - N << '\n';

    return 0;
}