import sys
sys.setrecursionlimit(10**6)
N=int(input())
g=[[] for i in range(N+1)]
id=dict()
for i in range(N):
    a,b=map(int,input().split())
    g[a].append(b)
    g[b].append(a)
    id[a+b*N]=i+1
    id[b+a*N]=i+1

ans=[]
vis=[-1]*(N+1)
stk=[]
def dfs(cur,par):
    vis[cur]=0
    stk.append((cur,par))
    for dst in g[cur]:
        if dst==par:
            continue
        if vis[dst]==-1:
            dfs(dst,cur)
        elif vis[dst]==0:
            ans.append(id[cur+dst*N])
            while stk:
                e=stk.pop()
                ans.append(id[e[0]+e[1]*N])
                if e[1]==dst:
                    break
    vis[cur]=1
    if stk:
        stk.pop()
dfs(1,0)
print(len(ans))
print(*ans)