#include <bits/stdc++.h>
using namespace std;
struct wf {
  int to, nxt;
} edge[100005 << 1];
int h[100005], vis[100005], is_top[200005], st[200005];
int val[100005], dep[100005], whe[200005], fa[100005];
int n, m, cnt, pos, flag, top;
void add(int u, int v) {
  edge[++cnt].nxt = h[u];
  edge[cnt].to = v;
  h[u] = cnt;
}
void dfs(int u, int ff, int dd) {
  dep[u] = dd;
  fa[u] = ff;
  vis[u] = 1;
  for (int i = h[u]; i != -1; i = edge[i].nxt) {
    int v = edge[i].to;
    if (!vis[v]) is_top[i] = 1, whe[v] = i, dfs(v, u, dd + 1);
  }
}
void DFS(int u) {
  vis[u] = 1;
  for (int i = h[u]; i != -1; i = edge[i].nxt) {
    int v = edge[i].to;
    if (is_top[i]) DFS(v), val[u] += val[v];
  }
}
int main() {
  cnt = -1;
  scanf("%d%d", &n, &m);
  int u, v;
  memset(edge, -1, sizeof(edge));
  memset(h, -1, sizeof(h));
  for (int i = 1; i <= m; i++) {
    scanf("%d%d", &u, &v);
    add(u, v);
    add(v, u);
  }
  for (int i = 1; i <= n; i++)
    if (!vis[i]) {
      dfs(i, 0, 1);
    }
  for (int i = 0; i <= cnt; i += 2)
    if (is_top[i] == 0 && is_top[i + 1] == 0) {
      int u = edge[i].to;
      int v = edge[i + 1].to;
      if (dep[v] > dep[u]) swap(u, v);
      ++val[u];
      --val[v];
    }
  memset(vis, 0, sizeof(vis));
  for (int i = 1; i <= n; i++)
    if (!vis[i]) DFS(i);
  for (int i = 0; i <= cnt; i += 2)
    if (is_top[i] == 0 && is_top[i + 1] == 0) {
      flag = 0;
      int u = edge[i].to;
      int v = edge[i + 1].to;
      if (dep[v] > dep[u]) swap(u, v);
      pos = u;
      while (1) {
        if (fa[pos] == v) break;
        if (val[pos] != 1) {
          flag = 1;
          break;
        }
        pos = fa[pos];
      }
      if (val[pos] == 1 && flag == 0) {
        st[++top] = i + 2 >> 1;
        while (u != v) {
          st[++top] = whe[u] + 2 >> 1;
          u = fa[u];
        }
      }
    }
  printf("%d\n", top);
  sort(st + 1, st + top + 1);
  for (int i = 1; i <= top; i++) printf("%d ", st[i]);
  return 0;
}
