from collections import defaultdict, deque


def lowlink(n, adj):
    bridges = []
    articulation_points = []
    used = [False] * n
    order = [0] * n
    low = [0] * n

    def dfs(now, parent, count):
        used[now] = True
        order[now] = count
        low[now] = order[now]
        count += 1
        isarticulation = False  # 間接点か
        nchildren = 0
        for to in adj[now]:
            if used[to]:
                # 訪問済みの頂点 = 後退辺
                if to != parent:
                    low[now] = min(low[now], order[to])
            else:
                nchildren += 1
                count = dfs(to, now, count)
                if to != parent:
                    low[now] = min(low[now], low[to])
                if parent != -1 and order[now] <= low[to]:
                    isarticulation = True
                if order[now] < low[to]:
                    bridges.append((now, to))

        if parent == -1 and nchildren >= 2:
            isarticulation = True
        if isarticulation:
            articulation_points.append(now)
        return count

    count = 0
    for i in range(n):
        if used[i]: continue
        count = dfs(i, -1, count)

    return bridges, articulation_points


N = int(input())

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

bridges, _ = lowlink(N, adj)

bs = set(bridges)
ans = []
for a, b in edge2id.keys():
    if (a, b) in bs: continue
    if (b, a) in bs: continue
    ans.append(edge2id[a, b] + 1)

print(len(ans))
print(*ans)