class UnionFind(): def __init__(self, n): self.n = n self.parents = [-1] * n self.group = n def find(self, x): if self.parents[x] < 0: return x else: self.parents[x] = self.find(self.parents[x]) return self.parents[x] def union(self, x, y): x = self.find(x) y = self.find(y) if x == y: return self.group -= 1 if self.parents[x] > self.parents[y]: x, y = y, x self.parents[x] += self.parents[y] self.parents[y] = x def size(self, x): return -self.parents[self.find(x)] def same(self, x, y): return self.find(x) == self.find(y) def members(self, x): root = self.find(x) return [i for i in range(self.n) if self.find(i) == root] def roots(self): return [i for i, x in enumerate(self.parents) if x < 0] def group_count(self): return self.group def all_group_members(self): dic = {r:[] for r in self.roots()} for i in range(self.n): dic[self.find(i)].append(i) return dic def __str__(self): return '\n'.join('{}: {}'.format(r, self.members(r)) for r in self.roots()) n = int(input()) edges = [[] for _ in range(n)] UF = UnionFind(n) for i in range(1, n + 1): a, b = map(int, input().split()) a -= 1 b -= 1 if UF.same(a, b): aa, bb, ii = a, b, i else: UF.union(a, b) edges[a].append((b, i)) edges[b].append((a, i)) used = [False] * n used[0] = 0 stack = [0] parent = [-1] * n bind = [-1] * n dist = [0] * n while stack: pos = stack.pop() for npos, i in edges[pos]: if used[npos]: continue used[npos] = True bind[npos] = i dist[npos] = dist[pos] + 1 parent[npos] = pos stack.append(npos) ans = [ii] if dist[aa] < dist[bb]: aa, bb = bb, aa while dist[aa] != dist[bb]: ans.append(bind[aa]) aa = parent[aa] while aa != bb: ans.append(bind[aa]) aa = parent[aa] ans.append(bind[bb]) bb = parent[bb] print(len(ans)) print(*ans)