#include <fstream>
#include <vector>
#include <algorithm>
using namespace std;

vector<int>dsu;

void MakeSet(int n) {
	dsu.resize(n);
	for (int i = 0; i < n; i++) {
		dsu[i] = i;
	}
}

int Find(int x) {
	return (dsu[x] == x) ? x : dsu[x] = Find(dsu[x]);
}

void Union(int a, int b) {
	a = Find(a);
	b = Find(b);
	if (rand() % 2) {
		swap(a, b);
	}
	dsu[a] = b;
}

int main() {
	ifstream fin("maxincycle.in");
	ofstream fout("maxincycle.out");
	int n, m, a, b;
	fin >> n >> m;
	MakeSet(n);
	vector<pair<int, int>>v;
	vector<int>answers;
	for (int i = 0; i < m; i++) {
		fin >> a >> b;
		v.push_back({ a - 1, b - 1 });
	}
	for (int i = 0; i < v.size(); ++i) {
		if (Find(v[i].first) != Find(v[i].second)) {
			Union(v[i].first, v[i].second);
			answers.push_back(i);
		}
	}
	fout << answers.size() << endl;
	for (int i = 0; i < answers.size(); i++) {
		fout << answers[i] + 1 << " ";
	}
}