#include <bits/stdc++.h>

template <typename T>
void rd(T& x){
	x = 0; char c = getchar(); int f = 1;
	while(!isdigit(c)) f = c == '-' ? -1 : 1, c = getchar();
	while(isdigit(c)) x = x * 10 + c - '0', c = getchar();
	x *= f;
}
template <typename T, typename... Args>
void rd(T& x, Args&... args){rd(x); rd(args...);}
template <typename T>
void wt(T x, char ed){
	if(x < 0) putchar('-'), x = -x;
	static short st[20], tp;
	do st[++tp] = x % 10, x /= 10; while(x);
	while(tp) putchar(st[tp--] + '0');
	putchar(ed);
}

using ll = long long;
const int N = 2e5 + 10;
const ll INF = 0x3f3f3f3f3f3f3f3f;

int n1, n2, m, S, T;

struct edge{
	int u, v; ll w;
}e[N << 1];
int head[N], cnte = 1;

void adde(int u, int v, ll w){
	e[++cnte] = {head[u], v, w}, head[u] = cnte;
	e[++cnte] = {head[v], u, 0}, head[v] = cnte;
}

int dis[N], cur[N];
bool bfs(){
	memset(dis, 0, sizeof dis);
	std::queue <int> q;
	dis[S] = 1, q.push(S), cur[S] = head[S];
	while(q.size()){
		int x = q.front(); q.pop();
		for(int i = head[x]; i; i = e[i].u){
			int y = e[i].v;
			if(!dis[y] && e[i].w){
				dis[y] = dis[x] + 1, cur[y] = head[y];
				q.push(y);
			}
		}
	}
	return dis[T];
}
ll dfs(int x, ll lim){
	if(x == T || !lim) return lim;
	ll ret = 0;
	for(int i = cur[x], k; i && lim; i = e[i].u){
		int y = e[i].v;
		cur[x] = i;
		if(dis[y] == dis[x] + 1){
			k = dfs(y, std::min(lim, e[i].w));
			e[i].w -= k, e[i ^ 1].w += k, ret += k, lim -= k;
		}
	}
	return ret;
}

ll dinic(){
	ll flow = 0;
	while(bfs()) flow += dfs(S, INF);
	return flow;
}

int main(){
	rd(n1, n2, m);
	S = n1 + n2 + 1, T = n1 + n2 + 2;
	for(int i = 1, u, v; i <= m; ++i){
		rd(u, v), ++u, ++v;
		adde(u, v + n1, 1);
	}
	for(int i = 1; i <= n1; ++i) adde(S, i, 1);
	for(int i = 1; i <= n2; ++i) adde(i + n1, T, 1);
	int ans = dinic();
	wt(ans, '\n');
	for(int i = 1; i <= n1; ++i){
		for(int j = head[i]; j; j = e[j].u){
			int y = e[j].v;
			if(y > n1 && y <= n1 + n2 && !e[j].w) wt(i - 1, ' '), wt(y - n1 - 1, '\n');
		}
	}
	return 0;
}