#include <bits/stdc++.h>
const int inf=2e9;
using namespace std;
mt19937 rng(time(0));
namespace io{
	const int SIZE = (1 << 24) + 1;
	char ibuf[SIZE], *iS, *iT;
	char obuf[SIZE], *oS = obuf, *oT = oS + SIZE - 1, c, qu[55];
	int f, qr;
	
	#define gc() (iS == iT ? (iT = (iS = ibuf) + fread (ibuf, 1, SIZE, stdin), (iS == iT ? EOF : *iS ++)) : *iS ++)
	
	inline void flush () {
		fwrite (obuf, 1, oS - obuf, stdout);
		oS = obuf;
	}
	
	inline void putc (char x) {
		*oS ++ = x;
		if (oS == oT) flush ();
	}
	
	template <class I>
	inline void read (I &x) {
		for (f = 1, c = gc(); c < '0' || c > '9'; c = gc()) if (c == '-') f = -1;
		for (x = 0; c <= '9' && c >= '0'; c = gc()) x = x * 10 + (c & 15); 
		x = f == -1 ? -x : x;
	}
	
	template <class I>
	inline void print (I x) {
		if (!x) putc ('0'); if (x < 0) putc ('-'), x = -x;
		while (x) qu[++ qr] = x % 10 + '0',  x /= 10;
		while (qr) putc (qu[qr --]);
	}
	
	struct Flusher_ {~Flusher_(){flush();}}io_flusher_;
}
using io :: read;
using io :: putc;
using io :: print;
int n,m,e,head[2000010],o=0,L[2000010],R[2000010],Ld[2000010],Rd[2000010],Lid[2000010];
bool vis[2000010];
struct edge{
	int to,link;
}E[2000010];
queue<int>q;
void add_edge(int u,int v){
	E[++o]={v,head[u]},head[u]=o;
}
bool bfs(){
	fill(Ld+1,Ld+n+1,0);
	fill(Rd+1,Rd+m+1,0);
	while(q.size()) q.pop();
	for(int i=1;i<=n;i++) if(!L[i]) q.push(i),Ld[i]=1;
	int dis=inf;
	while(q.size()){
		int u=q.front();q.pop();
		if(Ld[u]>dis) break;
		for(int i=head[u],v;i;i=E[i].link) if(!Rd[v=E[i].to]){
			Rd[v]=Ld[u]+1;
			if(!R[v]) dis=Rd[v];
			else{
				Ld[R[v]]=Rd[v]+1,q.push(R[v]);
			}
		}
	}
	return dis<inf;
}
bool dfs(int u){
	for(int i=head[u];i;i=E[i].link){
		int v=E[i].to;
		if(!vis[v]&&Rd[v]==Ld[u]+1){
			vis[v]=1;
			if(R[v]&&Rd[v]==inf) continue;
			if(!R[v]||dfs(R[v])){
				L[R[v]=u]=v;
				Lid[u]=i;
				return 1;
			}
		}
	}
	return 0;
}
int u[2000010],v[2000010],p[2000010];
int main(){
//	freopen("a.in","r",stdin);
//	freopen("a.out","w",stdout);
	read(n),read(m),read(e);
	iota(p+1,p+e+1,1),shuffle(p+1,p+e+1,rng);
	for(int i=1;i<=e;i++) read(u[i]),read(v[i]);
	for(int i=1;i<=e;i++){
		E[p[i]]={v[p[i]],head[u[p[i]]]},head[u[p[i]]]=p[i];
	}
	int ans=0;
	for(int _=0;(double)clock()/CLOCKS_PER_SEC<3.0&&_<19&&bfs();_++){
		fill(vis+1,vis+m+1,0);
		for(int i=1;i<=n;i++) if(!L[i]&&dfs(i)) ans++;
	}
	print(ans),putc('\n');
	for(int i=1;i<=n;i++) if(Lid[i]) print(Lid[i]),putc('\n');
}