#include <bits/stdc++.h>
using namespace std;
int n, m, tot, num, dfn[100010], low[100010], a[100010];
int cnt = 1, head[100010], to[200010], nxt[200010];
bool used[100010], vis[100010];
vector<int> v[100010];
stack<int> q, st;
void add(int x, int y) {
  cnt++;
  to[cnt] = y;
  nxt[cnt] = head[x];
  head[x] = cnt;
}
void tarjan(int x) {
  tot++;
  dfn[x] = low[x] = tot;
  st.push(x);
  for (int i = head[x]; i; i = nxt[i]) {
    if (vis[i >> 1]) {
      continue;
    }
    int y = to[i];
    q.push(i >> 1);
    vis[i >> 1] = true;
    if (!dfn[y]) {
      tarjan(y);
      low[x] = min(low[x], low[y]);
      if (dfn[x] > low[y]) {
        continue;
      }
      num++;
      int z;
      do {
        z = st.top();
        st.pop();
        a[num]++;
      } while (z != y);
      a[num]++;
      do {
        z = q.top();
        q.pop();
        v[num].push_back(z);
      } while (z != (i >> 1));
    } else {
      low[x] = min(low[x], dfn[y]);
    }
  }
}
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= m; i++) {
    int x, y;
    scanf("%d%d", &x, &y);
    add(x, y);
    add(y, x);
  }
  for (int i = 1; i <= n; i++) {
    if (!dfn[i]) {
      tarjan(i);
      st.pop();
    }
  }
  int ans = 0;
  for (int i = 1; i <= num; i++) {
    if (a[i] != (int)v[i].size()) {
      continue;
    }
    ans += a[i];
    for (int j = 0; j < a[i]; j++) {
      used[v[i][j]] = true;
    }
  }
  printf("%d\n", ans);
  for (int i = 1; i <= m; i++) {
    if (used[i]) {
      printf("%d ", i);
    }
  }
  return 0;
}
