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;
int n, m;
int ans = 0;
struct edge {
  int to, nxt, id;
} e[100010 << 1];
int edgenum = 0;
int lin[100010] = {0};
void add(int a, int b, int c) {
  ++edgenum;
  e[edgenum].to = b;
  e[edgenum].id = c;
  e[edgenum].nxt = lin[a];
  lin[a] = edgenum;
  ++edgenum;
  e[edgenum].to = a;
  e[edgenum].id = c;
  e[edgenum].nxt = lin[b];
  lin[b] = edgenum;
  return;
}
int dcc = 0;
vector<int> dcce[100010];
int siz[100010];
int dfn[100010], low[100010], tot = 0;
bool tag[100010], used[100010];
stack<int> ps;
stack<int> es;
void tarjan(int k) {
  dfn[k] = low[k] = ++tot;
  ps.push(k);
  for (int i = lin[k]; i != 0; i = e[i].nxt) {
    if (used[e[i].id]) continue;
    used[e[i].id] = true;
    es.push(e[i].id);
    if (dfn[e[i].to] == 0) {
      tarjan(e[i].to);
      low[k] = min(low[k], low[e[i].to]);
      if (low[e[i].to] >= dfn[k]) {
        ++dcc;
        int t;
        do {
          t = ps.top();
          ps.pop();
          ++siz[dcc];
        } while (t != e[i].to);
        ++siz[dcc];
        do {
          t = es.top();
          es.pop();
          dcce[dcc].push_back(t);
        } while (e[i].id != t);
      }
    } else
      low[k] = min(low[k], dfn[e[i].to]);
  }
  return;
}
int main() {
  scanf("%d%d", &n, &m);
  int a, b;
  for (int i = 1; i <= m; ++i) {
    scanf("%d%d", &a, &b);
    add(a, b, i);
  }
  for (int i = 1; i <= n; ++i) {
    if (dfn[i] == 0) {
      tarjan(i);
      ps.pop();
    }
  }
  for (int i = 1; i <= dcc; ++i) {
    if (siz[i] == dcce[i].size()) {
      for (int j = 0; j < dcce[i].size(); ++j) {
        tag[dcce[i][j]] = true;
        ++ans;
      }
    }
  }
  cout << ans << endl;
  for (int i = 1; i <= m; ++i) {
    if (tag[i]) {
      printf("%d ", i);
    }
  }
  puts("");
  return 0;
}
