A

#include <algorithm>
#include <iostream>
#include <array>
#include <vector>
#include <numeric>
#include <random>
#include <chrono>
#include <set>
#include <map>

#define int long long
using namespace std;

const long long INF = 1e9 + 7;
const int MAXN = 2e4 + 1000;
const int N = 1e5 + 10;

vector<vector<pair<int, int>>> g;
array<int, MAXN> used, tin, up;
int timer = 0;
vector<int> ans;

void dfs(int v, int e = -1) {
    used[v] = true;
    tin[v] = up[v] = timer++;
    for (auto [to, num]: g[v]) {
        if (num == e) {
            continue;
        }
        if (used[to]) {
            up[v] = min(up[v], tin[to]);
        } else {
            dfs(to, num);
            up[v] = min(up[v], up[to]);
            if (up[to] > tin[v]) {
                ans.emplace_back(num);
            }
        }
    }
}

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int n, m;
    cin >> n >> m;
    g.resize(n);
    for (int i = 0; i < m; ++i) {
        int u, v;
        cin >> u >> v;
        --u, --v;
        g[u].emplace_back(v, i);
        g[v].emplace_back(u, i);
    }

    for (int i = 0; i < n; ++i) {
        if (!used[i]) {
            dfs(i);
        }
    }
    cout << ans.size() << '\n';
    sort(ans.begin(), ans.end());
    for (auto& i: ans) {
        cout << i + 1 << '\n';
    }
}