import sys
sys.setrecursionlimit(10**6)
N=int(input())
g=[[] for i in range(N+1)]
d=[0]*(N+1)
e=[]
ok=[True]*(N+1)
id=dict()
for i in range(N):
    a,b=map(int,input().split())
    g[a].append(b)
    g[b].append(a)
    d[a]+=1
    d[b]+=1
    e.append((a,b))
stk=[]
for i in range(N):
    if d[i+1]==1:
        stk.append(i+1)
while stk:
    v=stk.pop()
    if d[v]<=0:
        continue
    for u in g[v]:
        d[u]-=1
        d[v]-=1
        if d[u]==1:
            stk.append(u)
ans=[]
for i in range(N):
    if d[e[i][0]]>0 and d[e[i][1]]>0:
        ans.append(i+1)
print(len(ans))
print(*ans)