#include<bits/stdc++.h>
#define int long long
#define ffor(i,a,b) for(int i=(a);i<=(b);i++)
#define roff(i,a,b) for(int i=(a);i>=(b);i--)
using namespace std;
const int MAXN=100000+10,MAXM=1000000+10;
int L,R,m,s,t,ans,tmp,tot=1,hd[MAXN],cur[MAXN],dis[MAXN];
struct Edge {int to,nxt,w;}edge[MAXM<<1];
void add_edge(int u,int v,int w) {
	edge[++tot]={v,hd[u],w},hd[u]=tot;
	edge[++tot]={u,hd[v],0},hd[v]=tot;
	return ;	
}
int bfs(void) {
	memset(dis,-1,sizeof(dis));
	queue<int> q;
	dis[s]=0,q.push(s);
	while(!q.empty()) {
		int u=q.front();
		q.pop(),cur[u]=hd[u];
		for(int i=hd[u];i;i=edge[i].nxt) {
			int to=edge[i].to,w=edge[i].w;
			if(!w||dis[to]!=-1) continue ;
			dis[to]=dis[u]+1,q.push(to);	
		}
	}
	return dis[t]!=-1;
}
int dinic(int u,int mx) {
	if(u==t) return mx;
	int res=0;
	for(int i=cur[u];i;i=edge[i].nxt,cur[u]=i) {
		int to=edge[i].to,w=edge[i].w;
		if(dis[to]!=dis[u]+1||!w) continue ;
		int tmp=dinic(to,min(w,mx));
		if(tmp) {
			edge[i].w-=tmp,edge[i^1].w+=tmp,mx-=tmp,res+=tmp;
			if(!mx) break ;
		}
		else dis[to]=-1;
	}
	return res;
}
signed main() {
	ios::sync_with_stdio(false),cin.tie(0),cout.tie(0);
	cin>>L>>R>>m,s=0,t=L+R+1;
	ffor(i,1,m) {
		int u,v;
		cin>>u>>v;
		u++,v++,add_edge(u,v+L,1);	
	}
	ffor(i,1,L) add_edge(s,i,1);
	ffor(i,L+1,L+R) add_edge(i,t,1);
	while(bfs()) while(dinic(s,1000000));
	vector<pair<int,int>> ans;
	ffor(u,1,L) for(int i=hd[u];i;i=edge[i].nxt) {
		int to=edge[i].to,w=edge[i].w;
		if(to>=L+1&&to<=L+R&&!w) ans.push_back({u-1,to-L-1});	
	}
	cout<<ans.size()<<'\n';
	for(auto pr:ans) cout<<pr.first<<' '<<pr.second<<'\n';
	return 0;
}