#include <iostream>
#include <vector>
using namespace std;
using ll=long long;

int main(){
  ll N,M;
  cin>>N>>M;
  vector<ll> V(N);
  vector<ll> ans;
  for(ll i=0;i<M;i++){
    ll u,v;
    cin>>u>>v;
    u--;
    v--;
    if(V[u]==0 && V[v]==0){
      V[u]=1;
      V[v]=1;
      ans.push_back(i+1);
    }
  }
  cout<<ans.size()<<endl;
  for(ll i:ans){
    cout<<i<<endl;
  }
}