// Problem: 18. 二分图最大匹配
// URL: https://qoj.ac/contest/1536/problem/898
// Writer: WRuperD
// Powered by CP Editor (https://cpeditor.org)

#include<bits/stdc++.h>
using namespace std;
const long long inf = 1e18;
const int mininf = 1e9 + 7;
#define int long long
#define pb emplace_back
inline int read(){int x=0,f=1;char ch=getchar();while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}while(ch>='0'&&ch<='9'){x=(x<<1)+(x<<3)+(ch^48);ch=getchar();}return x*f;}
inline void write(int x){if(x<0){x=~(x-1);putchar('-');}if(x>9)write(x/10);putchar(x%10+'0');}
#define put() putchar(' ')
#define endl puts("")
const int MAX = 2e6 + 10;
int n, m, s, t;

struct node{
	int v, w, cp;
}; vector <node> g[MAX];

int dis[MAX];

bool bfs(){
	for(int i = 1; i <= n; i++)	dis[i] = mininf;
	dis[s] = 0;
	queue <int> q;
	q.push(s);
	while(!q.empty()){
		int u = q.front();
		q.pop();
		for(auto V : g[u]){
			if(V.w > 0 and dis[V.v] > dis[u] + 1){
				dis[V.v] = dis[u] + 1;
				q.push(V.v);
			}
		}
	}
	if(dis[t] == mininf)	return 0;
	return 1;
}

int cur[MAX];

int aug(int u, int now){
	if(u == t)	return now;
	int ans = 0;
	for(int &i = cur[u]; i < g[u].size(); i++){
		int v = g[u][i].v, w = g[u][i].w, cp = g[u][i].cp;
		if(dis[v] != dis[u] + 1)	continue;
		int ret = aug(v, min(w, now));
		g[u][i].w -= ret, g[v][cp].w += ret;
		now -= ret, ans += ret;
		if(now <= 0)	break;
	}
	return ans;
}

void add_edge(int u, int v, int w){
	g[u].pb(node{v, w, g[v].size()});
	g[v].pb(node{u, 0, g[u].size() - 1});
}

void solve(){
	n = read(), m = read();
	int e = read();
	for(int i = 1; i <= e; i++){
		int u = read() + 1, v = read() + 1;
		add_edge(u + 1, n + v + 1, 1);
	}	
	for(int i = 1; i <= n; i++){
		add_edge(1, i + 1, 1);
	}
	for(int i = 1; i <= m; i++){
		add_edge(n + i + 1, n + m + 2, 1);
	}
	int n2 = n;
	n = n + m + 2;
	s = 1, t = n;
	int ans = 0;
	while(bfs()){
		for(int i = 1; i <= n; i++)	cur[i] = 0;
		ans += aug(1, inf);
	}
	write(ans), endl;
	for(int u = 1; u <= n2; u++){
		for(auto V : g[u]){
			if(V.w == 0 and V.v - n2 - 1 - 1 >= 0){
				write(u - 1 - 1), put(), write(V.v - n2 - 1 - 1), endl;
			}
		}
	}
}

signed main(){
	int t = 1;
	while(t--)	solve();
	return 0;
}