use std::collections::HashSet;

use proconio::input;

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

    for i in 0..n {
        if a[i] == 0 {
            println!("1\n{}", i + 1);
            return;
        }
    }

    let n = n.min(100);
    let mut mat = vec![vec![0; n]; D];
    for i in 0..n {
        for j in 0..D {
            if a[i] & (1 << j) != 0 {
                mat[j][i] = 1;
            }
        }
    }

    // show(&mat);
    let mut rank = 0;
    let mut pivots = vec![];
    for i in 0..n {
        let Some(id)=(rank..D).find(|&ii|mat[ii][i]==1)else{
            continue;
        };
        pivots.push((rank, i));
        for j in 0..n {
            let tmp = mat[rank][j];
            mat[rank][j] = mat[id][j];
            mat[id][j] = tmp;
        }

        for ii in 0..D {
            if ii == rank || mat[ii][i] == 0 {
                continue;
            }

            for j in 0..n {
                mat[ii][j] ^= mat[rank][j];
            }
        }

        rank += 1;
        // show(&mat);
    }

    if rank == n {
        println!("-1");
        return;
    }

    let mut ans = HashSet::new();
    for &(py, px) in pivots.iter() {
        for i in px..n {
            if mat[py][i] == 0 {
                continue;
            }

            ans.insert(i + 1);
        }
    }

    println!("{}", ans.len());
    for i in ans {
        print!("{} ", i);
    }
    println!()
}