#include<bits/stdc++.h>

using namespace std;

vector<int> ans;
vector<vector<pair<int, int>>> g;
vector<int> tin;
vector<int> tup;
int c = 1;


void dfs(int v, int p){
    tin[v] = c++;
    tup[v] = tin[v];
    for(auto to:g[v]){
        int u = to.first;
        if(u == p) continue;
        if(tin[u] > 0){
            tup[v] = min(tup[v], tin[u]);
        }
        else{
            dfs(u, v);
            tup[v] = min(tup[v], tup[u]);
            if(tup[u] > tin[v]){
                ans.push_back(to.second);
            }
        }
    }
}

int main(){
    int n, m;
    cin >> n >> m;
    for(int i = 0; i < n; ++i){
        g.push_back({});
        tup.push_back(0);
        tin.push_back(0);
    }
    for(int i = 1; i <= m; ++i){
        int u, v;
        cin >> u >> v;
        g[u - 1].push_back({v - 1, i});
        g[v - 1].push_back({u - 1, i});
    }
    for(int i = 0; i < n; ++i){
        if(tin[i] == 0)
            dfs(i, -1);
    }
    sort(ans.begin(), ans.end());
    cout << ans.size() << "\n";
    for(int i = 0; i < ans.size(); ++i){
        cout << ans[i] << "\n";
    }
}