#include <iostream>
#include <algorithm>
#include <vector>
#include <unordered_map>

using namespace std;

#include <cstdio>
struct Edge {
    int from;
    int to;
    int number;
};
vector <Edge> edges[20002];

vector<int> wow;
int timee = 0;
int tin[20002];
int dp[20002];
int used[20002];
vector <Edge> ans;



void dfs(int v, Edge kill_me)
{
    int parent = kill_me.to;

    used[v] = 1;
    tin[v] = dp[v] = timee++;
    for (auto e : edges[v]) {
        if (e.to == parent) continue;
        if (used[e.to] == 1)
            dp[v] = min(dp[v], tin[e.to]);
        else {
            dfs(e.to, e);
            dp[v] = min(dp[v], dp[e.to]);
            if (dp[e.to] > tin[v])
                ans.push_back(kill_me);
        }
    }
}


int main()
{
    int n, m;
    cin >> n >> m;
    for (int i = 1; i <= m; ++i)
    {
        int u, v; cin >> u >> v;
        Edge e;
        e.from = u; e.to = v; e.number = i;
        edges[u].push_back(e);
        e.from = v; e.to = u; e.number = i;
        edges[v].push_back(e);
    }
    timee = 0;
    Edge weird; weird.to = 100000; weird.from = 2000000; weird.number = -1;
    for (int i = 1; i <= n; ++i)
        if (used[i] == 0)
            dfs(i, weird);
    cout <<"size = "  << ans.size() << '\n';

    int array[ans.size()];
    for (int i = 0; i < ans.size(); ++i) {
        array[i] = ans[i].number;
    }
    sort(array, array + ans.size());
    for (int i = 0; i < ans.size(); ++i) {
        cout << array[i] << '\n';
    }
    return 0;
}