import io
import sys
from collections import defaultdict, deque, Counter
from itertools import permutations, combinations, accumulate
from heapq import heappush, heappop
from bisect import bisect_right, bisect_left
from math import gcd
import math

_INPUT = """\
6
4
2 0 2 4
3
2024 20 24
"""

def elimination(A,N=60):
  used=[0]*len(A)
  K=[[0]*i+[1]+[0]*(len(A)-i-1) for i in range(len(A))]
  for i in reversed(range(N)):
    f=0
    for j in range(len(A)):
      if (A[j]>>i)&1==1 and used[j]==0:
        if f==0:
          x=A[j]
          used[j]=1
          m=K[j].copy()
          f=1
        else:
          A[j]^=x
          for k in range(len(A)):
            if m[k]==1:
              K[j][k]^=1
  return K,A

def input():
  return sys.stdin.readline()[:-1]

def solve(test):
  N=int(input())
  A=list(map(int, input().split()))
  K,A=elimination(A[:61])
  flg=0
  for i in range(min(len(A),61)):
    if A[i]==0:
      M=K[i].count(1)
      print(M)
      print(*[j+1 for j in range(len(A)) if K[i][j]==1])
      flg=1
      break
  if flg==0:
    print(-1)

def random_input():
  from random import randint,shuffle
  N=randint(1,10)
  M=randint(1,N)
  A=list(range(1,M+1))+[randint(1,M) for _ in range(N-M)]
  shuffle(A)
  return (" ".join(map(str, [N,M]))+"\n"+" ".join(map(str, A))+"\n")*3

def simple_solve():
  return []

def main(test):
  if test==0:
    solve(0)
  elif test==1:
    sys.stdin = io.StringIO(_INPUT)
    case_no=int(input())
    for _ in range(case_no):
      solve(0)
  else:
    for i in range(1000):
      sys.stdin = io.StringIO(random_input())
      x=solve(1)
      y=simple_solve()
      if x!=y:
        print(i,x,y)
        print(*[line for line in sys.stdin],sep='')
        break

#0:提出用、1:与えられたテスト用、2:ストレステスト用
main(0)