#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int maxn = (int)4e5+5;
int n,m,s,t,L,R,lev[maxn],h[maxn]; queue<int> q;
struct Node{int to,c,rev;}; vector<Node> v[maxn];
void addEdge(int fr,int to,int c){
	int f=v[fr].size(), g=v[to].size();
	v[fr].push_back((Node){to,c,g}), v[to].push_back((Node){fr,0,f});
}
bool bfs(){
	while(!q.empty()) q.pop();
	for(int al=0;al<=n;al++) lev[al] = -1, h[al] = 0;
	lev[s] = 0; q.push(s);
	while(!q.empty()){
		int u = q.front(); q.pop();
		for(auto X:v[u])if(X.c && lev[X.to]==-1)
			lev[X.to] = lev[u]+1, q.push(X.to);
		if(~lev[t]) return 1;
	}
	return lev[t]!=-1;
}
int dfs(int u,int k){
	if(u==t || !k) return k;
	int ret = 0, sz = v[u].size();
	for(int al=h[u];al<sz;al++,h[u]=al)if(v[u][al].c){
		int to = v[u][al].to;
		if(lev[to]==lev[u]+1){
			int cur = dfs(to,min(k,v[u][al].c));
			v[u][al].c -= cur, v[to][v[u][al].rev].c += cur;
			k -= cur, ret += cur;
			if(!k) break;
		}
	}
	if(!ret) lev[u] = -1;
	return ret;
}
int main(){
    // freopen("a.in","r",stdin);
    ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
    cin >> L >> R >> m;
	s = 0, t = n = L+R+1; 
	for(int al=1;al<=L;al++) addEdge(0,al,1);
	for(int al=1;al<=R;al++) addEdge(al+L,L+R+1,1);
	for(int al=1,be,ga;al<=m;al++){
        cin >> be >> ga;
        addEdge(be+1,ga+L+1,1);
    }
		
	ll ans = 0;
	while(bfs()) ans += dfs(s,INT_MAX);
    cout << ans << endl;
	for(int al=1;al<=L;al++)
        for(auto X:v[al])
            if(X.to>L && !X.c){
                cout << al-1 << " " << X.to-L-1 << endl;
                break;
            }
	return 0;
}