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

int n, m, E, mch[100005], vis[100005];
vector<int> G[100005];

bool dfs(int x) {
	if (vis[x]) return 0; vis[x] = 1; 
  	for (int y : G[x])
    	if (!mch[y] || dfs(mch[y])) return mch[y] = x, 1;
	return 0;
}

int main(void) {
    ios::sync_with_stdio(0); 
  	cin >> n >> m >> E;
  	for(int i = 1; i <= E; i++) {
    	int u, v; cin >> u >> v; ++u; ++v; 
    	G[u].push_back(v);
  	}
  	int ans = 0;
  	for (int i = 1; i <= n; i++) if (dfs(i)) {
    	memset(vis, 0, sizeof(vis));
    	++ans; 
  	}
  	cout << ans << endl;
    for (int i = 1; i <= n; ++i)
        if (mch[i]) cout << i - 1 << " " << mch[i] - 1 << "\n"; 
  	return 0;
}