#include <iostream>
#include <vector>
#include <string>
#include <stack>
#include <set>
#include <map>
#include "optimization.h"

using namespace std;
vector<vector<int>> tree;
vector<bool> mark;
map<pair<int, int>, bool> rebra;
int n, e;
map<pair<int, int>, pair<int, int>> mem;
vector<int> time_;
vector<int> min_time;
int T = 0;
vector<int>result;
int dfs(int root, int parent) {
    time_[root] = min_time[root] = ++T;
    for (auto x : tree[root]) {
        if (x == parent) continue;
        if (time_[x] == 0){
            dfs(x, root);
            if (min_time[x] > time_[root]  && mem[{min(x, root), max(x,root)}].second == 1){
                result.push_back(mem[{min(x, root), max(x,root)}].first);
            }
            min_time[root] = min(min_time[root], min_time[x]);
        }
        else{
            min_time[root] = min(min_time[root], time_[x]);
        }
    }
}


int main() {
    cin >> n >> e;
    mark.resize(n+1, false);
    tree.resize(n+1);
    time_.resize(n+1);
    min_time.resize(n+1);
    for (int i = 1; i <= e; i++) {
        int a, b;
        cin >> a >> b;
        if (a > b){
            swap(a,b);
        }
        if (mem.count({a,b}) == 0){
            mem[{a, b}] = {i, 1};
        }
        else{
            mem[{a, b}].second += 1;
        }
        tree[a].push_back(b);
        tree[b].push_back(a);
    }
    dfs(1, 0);
    cout << result.size() << '\n';
    for (auto x : result){
        cout << x << '\n';
    }
}