#include <bits/stdc++.h>
using namespace std;
using ll = long long;
constexpr int N = 5e5 + 5;
constexpr int M = 4e6 + 5;

int head[N], to[M], nxt[M], tot = 1;
void add(int u, int v) {
    nxt[++tot] = head[u];
    head[u] = tot;
    to[tot] = v;
}
int dfn[N], low[N], timer; 
bool is_bridge[M>>1];

int n, m, cnt;

void tarjan(int u, int in_e) {
    dfn[u] = low[u] = ++timer; 
    for (int i = head[u]; i; i = nxt[i]) {
        if ((i ^ 1) == in_e) continue;
        int v = to[i];
        if (!dfn[v]) {
            tarjan(v, i);
            low[u] = std::min(low[u], low[v]);
            if (low[v] > dfn[u]) {
                is_bridge[i >> 1] = true;
                cnt++;
            }
        } else if (dfn[v] < dfn[u]) {
            low[u] = std::min(low[u], dfn[v]);
        }
    }
}
void fc() {
    std::cin >> n >> m;

    for (int i = 0; i < m; i++) {
        int u, v;
        std::cin >> u >> v;
        add(u, v);
        add(v, u);
    }

    for(int i=1;i<=n;i++)if(!dfn[i])tarjan(i,0);

    std::cout << cnt << "\n";
    for (int i = 1; i <= m; i++)
        if (is_bridge[i]) std::cout << i << " ";
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int t = 1;
    // std::cin>>t;
    while (t--) fc();
    return 0;
}