import os,sys,random,threading
#sys.exit() 退出程序
#sys.setrecursionlimit(10**6) #调整栈空间
from random import randint,choice,shuffle
#randint(a,b)从[a,b]范围随机选择一个数
#choice(seq)seq可以是一个列表,元组或字符串,从seq中随机选取一个元素
#shuffle(x)将一个可变的序列x中的元素打乱
from copy import deepcopy
from io import BytesIO,IOBase
from types import GeneratorType
from functools import lru_cache,reduce
#reduce(op,迭代对象)
from bisect import bisect_left,bisect_right
#bisect_left(x) 大于等于x的第一个下标
#bisect_right(x) 大于x的第一个下标
from collections import Counter,defaultdict,deque
from itertools import accumulate,combinations,permutations
#accumulate(a)用a序列生成一个累积迭代器，一般list化前面放个[0]做前缀和用
#combinations(a,k)a序列选k个 组合迭代器
#permutations(a,k)a序列选k个 排列迭代器
from heapq import  heapify,heappop,heappush
#heapify将列表转为堆
from typing import Generic,Iterable,Iterator,TypeVar,Union,List
from string import ascii_lowercase,ascii_uppercase,digits
#小写字母，大写字母，十进制数字
from math import ceil,floor,sqrt,pi,factorial,gcd,log,log10,log2,inf
#ceil向上取整，floor向下取整 ，sqrt开方 ，factorial阶乘
from decimal import Decimal,getcontext
#Decimal(s) 实例化Decimal对象,一般使用字符串
#getcontext().prec=100 修改精度
from sys import stdin, stdout, setrecursionlimit
input = lambda: sys.stdin.readline().rstrip("\r\n")
MI = lambda :map(int,input().split())
li = lambda :list(MI())
ii = lambda :int(input())
mod = int(1e9 + 7) #998244353
inf = 1<<60
py = lambda :print("YES")
pn = lambda :print("NO")
DIRS = [(0, 1), (1, 0), (0, -1), (-1, 0)]  # 右下左上
DIRS8 = [(0, 1), (1, 1), (1, 0), (1, -1), (0, -1), (-1, -1), (-1, 0),(-1, 1)]  # →↘↓↙←↖↑↗



# https://ac.nowcoder.com/acm/contest/vip-end-index?rankTypeFilter=-1&onlyCreateFilter=false&topCategoryFilter=13&categoryFilter=6&signUpFilter=&orderType=NO&page=2




n=ii()

a=li()

if 0 in a:
    print(1)
    print(a.index(0)+1)
    exit()


base=[0]*61 #位数
pos=[None for _ in range(61)]

def insert(x,idx): #插入一个数
    tmp=Counter()
    tmp[idx]+=1
    for i in range(60,-1,-1):
        if x>>i&1==0:
            continue
        if base[i]==0:
            base[i]=x
            pos[i]=tmp
            return 1
        x^=base[i]
        tmp+=pos[i]
    return 0

if n>65:
    n=65
    a=a[:n]

for idx in range(n):
    if insert(a[idx],idx)==0:
        ans=[idx+1]
        res=Counter()
        for i in range(60,-1,-1):
            if a[i]>>i&1:
                res+=pos[i]
                a[i]^=base[i]
        for i,c in res.items():
            if c%2==1:
                ans.append(i+1)
        print(len(ans))
        ans.sort()
        print(*ans)
        exit()


print(-1)