import sys
input = sys.stdin.readline

N = int(input())
G = [[] for i in range(N)]
deg = [0] * N
for i in range(N):
    a, b = map(int, input().split())
    a, b = a - 1, b - 1
    G[a].append((b, i))
    G[b].append((a, i))
    deg[a] += 1
    deg[b] += 1

Q = []
S = set()
for i in range(N):
    if deg[i] == 1:
        Q.append(i)

while Q:
    u = Q.pop()
    for v, i in G[u]:
        deg[v] -= 1
        if deg[v] == 1:
            Q.append(v)
        S.add(i)

ans = []
for i in range(N):
    if i not in S:
        ans.append(i + 1)

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