#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using ll = long long;
#define rep(i,n) for(ll i=0;i<(ll)(n);i++)
using mint = atcoder::modint998244353;

int main(){
	int n,m;
	cin>>n>>m;
	vector<int> stl(n,0),ans;
	rep(i,m){
		int u,v;
		cin>>u>>v;
		u--; v--;
		if(stl.at(u)==0&&stl.at(v)==0){
			stl.at(u)=1;
			stl.at(v)=1;
			ans.push_back(i+1);
		}
	}
	cout<<ans.size()<<endl;
	for(auto x:ans) cout<<x<<endl;
}