from collections import defaultdict, deque

N = int(input())

degs = [0] * N
edge2id = {}
adj = defaultdict(list)
for i in range(N):
    a, b = map(lambda x: int(x)-1, input().split())
    adj[a].append(b)
    adj[b].append(a)
    edge2id[a, b] = i
    edge2id[b, a] = i
    degs[a] += 1
    degs[b] += 1


q = deque()
for i in range(N):
    if degs[i] == 1:
        q.append(i)

while q:
    v = q.popleft()
    assert degs[v] == 1

    degs[v] -= 1
    for to in adj[v]:
        degs[to] -= 1
        if degs[to] == 1:
            q.append(to)

ans = set()
for u, v in edge2id.keys():
    if degs[u] > 0 and degs[v] > 0:
        ans.add(edge2id[u, v])

print(len(ans))
print(*[x+1 for x in ans])