import sys
sys.setrecursionlimit(10**7)

class LowLink:
  def __init__(self, g):
    self.n=len(g)
    self.used=[0]*n
    self.ords=[0]*n
    self.lows=[0]*n
    self.aps=[]
    self.bridges=[]
    self.k=0
    for i in range(self.n):
      if self.used[i]==0:
        self.k=self.dfs(i,self.k,-1)
  def dfs(self,id,k,par):
    self.used[id]=1
    k+=1
    self.ords[id]=k
    self.lows[id]=self.ords[id]
    is_aps=0
    count=0
    for v in g[id]:
      if self.used[v]==0:
        count+=1
        k=self.dfs(v,k,id)
        self.lows[id]=min(self.lows[id],self.lows[v])
        if par!=-1 and self.ords[id]<=self.lows[v]:
          is_aps=1
        if self.ords[id]<self.lows[v]:
          self.bridges.append((min(id,v),max(id,v)))
      elif v!=par:
        self.lows[id]=min(self.lows[id],self.ords[v])
    if par==-1 and count>=2:
      is_aps=1
    if is_aps==1:
      self.aps.append(id)
    return k

n=int(input())
g=[[] for _ in range(n)]
edges=[]
for i in range(1,n+1):
    a,b=map(int,input().split())
    a-=1
    b-=1
    edges.append([a,b,i])
    g[a].append(b)
    g[b].append(a)
ll=LowLink(g)
prior=set(ll.bridges)
ans=[]
for u,v,i in edges:
    if (u,v) in prior or (v,u) in prior:
        continue
    else:
        ans.append(i)
print(len(ans))
print(*ans)