#include <bits/stdc++.h>
#define pb emplace_back
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;

inline ll read() {
	ll ret = 0, w = 1; char c = getchar();
	while(!isdigit(c))	{if(c == '-')	w = -1; c = getchar();}
	while(isdigit(c))	{ret = (ret << 1) + (ret << 3) + (c ^ 48); c = getchar();}
	return ret * w;	
}

char buf[50];
inline void write(ll x) {
	if(x < 0)	x = -x, putchar('-');
	int tp = 0;
	do { buf[++tp] = x % 10 + 48; x /= 10;} while(x);
	while(tp)	putchar(buf[tp--]);
}

const int MAX_N = 2e5 + 10;
int n, m, e, cnt, match[MAX_N], vis[MAX_N];
pii ans[MAX_N];
vector<int> E[MAX_N];

bool dfs(int u, int tim) {
	if(vis[u] == tim)	return false;
	vis[u] = tim;
	for(int v : E[u])
		if(!match[v] || dfs(match[v], tim)) {
			match[v] = u;
			return true;
		}
	return false;
}

int main() {
	n = read(), m = read(), e = read();
	for(int i = 1, u, v; i <= e; i++) {
		u = read() + 1, v = read() + 1;
		E[u].pb(v);
	}
	for(int i = 1; i <= n; i++)
		dfs(i, i);
	for(int i = 1; i <= m; i++)
		if(match[i])	ans[++cnt] = make_pair(match[i], i);
	write(cnt), putchar('\n');
	for(int i = 1; i <= cnt; i++) {
		write(ans[i].first - 1), putchar(' ');
		write(ans[i].second - 1), putchar('\n');
	}
	
	return 0;
}