2 0
 100000 0
 8 9
1 2
2 3
3 4
4 1
5 6
6 7
7 8
8 5
6 8
 2 1
1 2
 11 9
5 9
8 5
11 3
11 1
3 4
7 11
3 1
11 2
7 2
 7 9
7 3
7 4
1 2
2 3
3 1
3 4
4 5
5 6
6 4
 7 5
5 4
7 3
7 1
6 7
3 1
 7 8
1 2
2 3
3 4
4 1
3 5
5 6
6 7
7 3
 6 9
1 2
2 3
1 4
4 2
5 2
5 3
4 5
6 4
6 5
 7 9
1 2
2 4
4 3
3 1
2 3
4 5
5 6
6 7
7 4
 1 0
 6 7
1 2
2 3
3 1
3 4
4 5
5 6
6 4
 4 5
1 2
2 3
3 4
4 1
1 3
 100000 3
99998 99999
99999 100000
100000 99998

0

 0

 4
1 2 3 4 
 0

 6
3 4 6 7 8 9 
 9
1 2 3 4 5 6 7 8 9 
 3
2 3 5 
 8
1 2 3 4 5 6 7 8 
 0

 4
6 7 8 9 
 0

 6
1 2 3 5 6 7 
 0

 3
1 2 3 

#include <bits/stdc++.h>
using namespace std;
const int NR = 1e5 + 10;
void Min(int& x, int y) { x = min(x, y); }
void Max(int& x, int y) { x = max(x, y); }
int n, m, ans;
int to[NR << 1], nxt[NR << 1], head[NR], tot = 1;
void add(int x, int y) { to[tot] = y, nxt[tot] = head[x], head[x] = tot++; }
int cnt;
int c[NR], num[NR];
int all, top;
int dfn[NR], low[NR];
int st[NR];
int sum[NR];
void tarjan(int x, int la) {
  dfn[x] = low[x] = ++all;
  st[++top] = x;
  for (int i = head[x]; i; i = nxt[i]) {
    int y = to[i];
    if (i == la * 2 - (la ^ 1)) continue;
    if (!dfn[y])
      tarjan(y, i), Min(low[x], low[y]);
    else
      Min(low[x], dfn[y]);
  }
  if (low[x] == dfn[x]) {
    int y = -1;
    cnt++;
    while (x != y) {
      y = st[top--];
      c[y] = cnt;
      num[cnt]++;
    }
  }
}
int read() {
  int x = 0, f = 1;
  char ch = getchar();
  while (ch > '9' || ch < '0') {
    if (ch == '-') f = -1;
    ch = getchar();
  }
  while (ch <= '9' && ch >= '0') {
    x = (x << 3) + (x << 1) + (ch ^ 48);
    ch = getchar();
  }
  return x * f;
}
int main() {
  n = read(), m = read();
  for (int i = 1, x, y; i <= m; i++)
    x = read(), y = read(), add(x, y), add(y, x);
  for (int i = 1; i <= n; i++)
    if (!dfn[i]) tarjan(i, 0);
  for (int i = 1; i < tot; i += 2) {
    int x = to[i], y = to[i + 1];
    if (c[x] == c[y]) sum[c[x]]++;
  }
  for (int i = 1; i <= cnt; i++)
    if (num[i] == sum[i]) ans += num[i];
  printf("%d\n", ans);
  for (int i = 1; i < tot; i += 2) {
    int x = to[i], y = to[i + 1];
    if (num[c[x]] == sum[c[x]] && c[x] == c[y]) printf("%d ", (i + 1) / 2);
  }
  return 0;
}
