use std::collections::HashSet;

use proconio::input;

fn main() {
    input! {
        n:usize,
        mut a:[usize;n],
    }
    const D: usize = 60;

    let mut hists = vec![];
    for i in 0..n {
        let mut hs = HashSet::new();
        hs.insert(i);
        hists.push(hs);
    }

    let mut rank = 0;
    for col in 0..D {
        let Some(row)=(rank..n).find(|&row|a[row]&(1<<col)!=0)else{
            continue;
        };

        hists.swap(row, rank);
        a.swap(row, rank);

        for i in 0..n {
            if rank == i || a[i] & (1 << col) == 0 {
                continue;
            }

            a[i] ^= a[rank];

            hists[i] = hists[i]
                .symmetric_difference(&hists[rank])
                .copied()
                .collect::<HashSet<_>>();
        }

        rank += 1;
    }

    if let Some(ind) = (0..n).find(|&i| a[i] == 0) {
        let ans = &hists[ind];
        println!("{}", ans.len());
        for bi in ans {
            print!("{} ", bi + 1);
        }
        println!();
    } else {
        println!("-1");
    }
}