#include<iostream>
#include<vector>
#include<fstream>
using namespace std;
int n, m, i, k, l, fr[20005],x,y, cuplat[20005],nr,cnt;
vector<vector<int>>mu;
void cupleaza(int a, int b) {
	cuplat[cuplat[a]] = 0;
	cuplat[cuplat[b]] = 0;
	cuplat[a] = b;
	cuplat[b] = a;
}
bool DFS(int nod) {
	fr[nod] = nr;
	for(auto j:mu[nod])
		if (fr[j] < nr) {
			fr[j] = nr;
			if (cuplat[j]) {
				if (DFS(cuplat[j])) {
					cupleaza(nod, j);
					return 1;
				}
			}
			else {
				cupleaza(nod, j);
				return 1;
			}
		}
	return 0;
}
int main() {
    ifstream cin("cuplaj.in");
    ofstream cout("cuplaj.out");
	cin >> n >> m>>k;
	mu.resize(n+m+2);
	for (i = 1;i <=k;i++) {
		cin >> x >> y;
		mu[x].emplace_back(y + n);
		mu[y + n].emplace_back(x);
	}
	bool ok=1;
	while (ok)
	{
		nr++;
		ok = 0;
		for (i = 1;i <= n+m;i++)
			if(cuplat[i]==0 and fr[i]<nr)
			ok |=DFS(i);
	}
	for (i = 1;i <= n;i++)
		if (cuplat[i] != 0) cnt++;
	cout << cnt << '\n';
	for (i = 1;i <= n;i++)
		if (cuplat[i] != 0)
			cout << i << ' ' << cuplat[i] - n << '\n';
}