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

used = [0]*n
q = [g[i][0] for i in range(n) if deg[i]==1]
while q:
    v,i = q.pop()
    if used[i]: continue
    used[i] = 1
    deg[v] -= 1
    if deg[v] == 1:
        q += g[v]

ans = [i+1 for i in range(n) if used[i]==0]
print(len(ans))
print(*ans)