#include<cstdio>
#include<vector>
#include<queue>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<ctime>
#include<random>
#include<array>
#include<assert.h>
#define pb emplace_back
#define mp make_pair
#define fi first
#define se second
#define dbg(x) cerr<<"In Line "<< __LINE__<<" the "<<#x<<" = "<<x<<'\n'
#define dpi(x,y) cerr<<"In Line "<<__LINE__<<" the "<<#x<<" = "<<x<<" ; "<<"the "<<#y<<" = "<<y<<'\n'
#define DE(fmt,...) fprintf(stderr, "Line %d : " fmt "\n",__LINE__,##__VA_ARGS__)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int>pii;
typedef pair<ll,int>pli;
typedef pair<ll,ll>pll;
typedef pair<int,ll>pil;
typedef vector<int>vi;
typedef vector<ll>vll;
typedef vector<pii>vpii;
typedef vector<pll>vpll;
template<typename T>T cmax(T &x, T y){return x=x>y?x:y;}
template<typename T>T cmin(T &x, T y){return x=x<y?x:y;}
template<typename T>
T &read(T &r){
	r=0;bool w=0;char ch=getchar();
	while(ch<'0'||ch>'9')w=ch=='-'?1:0,ch=getchar();
	while(ch>='0'&&ch<='9')r=r*10+(ch^48),ch=getchar();
	return r=w?-r:r;
}
template<typename T1,typename... T2>
void read(T1 &x,T2& ...y){read(x);read(y...);}
const int N=2000010;
mt19937 rnd(12321);
int A,B,m;
vpii eg[N];
int L[N],R[N];
int pos[N],pre[N],dis[N],ban[N];
int ans;
int solve(){
	queue<int>q;
	for(int i=1;i<=A;i++)dis[i]=N,pos[i]=pre[i]=ban[i]=0;
	for(int i=1;i<=A;i++)
		if(!R[i]){
			q.push(i);
			dis[i]=1;
		}
	while(!q.empty()){
		int x=q.front();q.pop();
		for(auto i:eg[x]){
			int y=i.fi;
			if(ban[y])continue;
			if(!L[y]){
				pos[x]=y;
				ban[y]=1;
				break;
			}
			int t=L[y];
			if(dis[t]>dis[x]+1){
				dis[t]=dis[x]+1;
				pre[t]=x;
				q.push(t);
			}
		}
	}
	int md=N;
	for(int i=1;i<=A;i++)if(pos[i])cmin(md,dis[i]);
	for(int i=1;i<=A;i++){
		if(pos[i]){
			int x=i,lst=pos[i];
			while(x){
				int tmp=R[x];
				R[x]=lst;
				L[lst]=x;
				lst=tmp;
				x=pre[x];
			}
			++ans;
		}
	}
	if(md==N)return 0;
	return 1;
}
signed main(){
	#ifdef do_while_true
		assert(freopen("data.in","r",stdin));
		assert(freopen("data.out","w",stdout));
	#endif
	read(A,B,m);
	for(int i=1;i<=m;i++){
		int u,v;read(u,v);
		eg[u].pb(v,i);
	}
	while(1.0*clock()/CLOCKS_PER_SEC<3.3){
		if(!solve())
			break;
	}
	cout<<ans<<'\n';
	for(int i=1;i<=A;i++)if(R[i])
		for(auto [j,id]:eg[i])
			if(j==R[i]){
				cout<<id<<'\n';
				break;
			}
    #ifdef do_while_true
//		cerr<<'\n'<<"Time:"<<1.0*clock()/CLOCKS_PER_SEC*1000<<" ms"<<'\n';
	#endif
	return 0;
}