#include<cstdio>
using namespace std;
typedef long long LL;
const int maxn = 1010;
LL a[maxn], n;
int main()
{
  freopen("asm_contribute.in", "r", stdin);
  freopen("asm_contribute.out", "w", stdout);
  scanf("%d", &n);
  for(LL i = 0; i < n; i++) 
    scanf("%d", &a[i]);
  for(LL s = 1; s < (1 << n); s++){
    LL now = 0, cnt = 0;
    for(LL i = 0; i < n; i++)
      if(s & (1 << i)){
        now ^= a[i]; cnt++;
      }
    if(now == 0){
      printf("%d\n", cnt);
      for(int i = 0; i < n; i++)
        if(s & (1 << i))
          printf("%d ", i + 1);
      puts("");
      break;
    }
  }
  return 0;
}