#include<bits/stdc++.h>
using namespace std;
const int N=1e5+10;
namespace Flow
{
	const int N=2e5+10,M=5e5+10;
	int hd[N],to[M],nx[M],F[M],tt=1,S,T;
	void link(int u,int v,int f)
	{
		to[++tt]=v,nx[tt]=hd[u],hd[u]=tt,F[tt]=f;
		to[++tt]=u,nx[tt]=hd[v],hd[v]=tt,F[tt]=0;
	}
	int dis[N],q[N],l,r,cur[N];
	bool bfs()
	{
		memset(dis,0x3f,sizeof dis);
		dis[S]=0;q[l=r=1]=S;
		while(l<=r)
		{
			int u=q[l++];
			for(int i=hd[u];i;i=nx[i])
			{
				int v=to[i];
				if(F[i]&&dis[v]>dis[u]+1)
				{
					dis[v]=dis[u]+1;
					q[++r]=v;
					if(v==T)return true;
				}
			}
		}
		return false;
	}
	int dfs(int u,int f)
	{
		if(u==T)return f;
		int r=f;
		for(int&i=cur[u];i;i=nx[i])
		{
			int v=to[i];
			if(F[i]&&dis[v]==dis[u]+1)
			{
				int k=dfs(v,min(F[i],r));
				F[i]-=k;F[i^1]+=k;
				r-=k;if(!r)break;
			}
		}
		if(r)dis[u]=0;
		return f-r;
	}
	int Dinic()
	{
		int flow=0;
		while(bfs())
		{
			memcpy(cur,hd,sizeof hd);
			flow+=dfs(S,10000000);
		}
		return flow;
	}
}
int U[N*2],V[N*2];
int main()
{
	cin.tie(0)->sync_with_stdio(0);
	int L,R,m;cin>>L>>R>>m;
	Flow::S=L+R+1,Flow::T=L+R+2;
	for(int i=1;i<=m;++i)
	{
		int u,v;cin>>u>>v;
		Flow::link(u+1,v+L+1,1);
		U[i]=u,V[i]=v;
	}
	for(int i=1;i<=L;++i)Flow::link(Flow::S,i,1);
	for(int i=1;i<=R;++i)Flow::link(L+i,Flow::T,1);
	int ans=Flow::Dinic();
	cerr<<ans<<endl;
	vector<pair<int,int>>W;
	for(int i=1;i<=m;++i)if(!Flow::F[i*2])
		W.emplace_back(U[i],V[i]);
	sort(W.begin(),W.end());
	cout<<W.size()<<endl;
	for(auto k:W)cout<<k.first<<" "<<k.second<<"\n";
}