#[allow(unused_imports)]
use std::cmp::Ordering;

#[allow(unused_imports)]
use std::collections::{BTreeMap, BTreeSet, BinaryHeap, HashMap, HashSet, VecDeque};

#[allow(unused_imports)]
use std::io::{stdin, stdout, BufWriter, Write};

#[allow(unused_imports)]
use std::iter::FromIterator;

#[allow(unused_macros)]
macro_rules! min {
    ($x: expr) => ($x);
    ($x: expr, $($z: expr),+) => {{
        std::cmp::min($x, min!($($z),*))
    }}
}

#[allow(unused_macros)]
macro_rules! max {
    ($x: expr) => ($x);
    ($x: expr, $($z: expr),+) => {{
        std::cmp::max($x, max!($($z),*))
    }}
}

#[allow(unused_macros)]
macro_rules! get {
    ([$t: ty]) => {
        {
            let mut line = String::new();
            stdin().read_line(&mut line).unwrap();
            line.split_whitespace().map(|t|t.parse::<$t>().unwrap()).collect::<Vec<_>>()
        }
    };
    ([$t: ty];$n: expr) => {
        (0..$n).map(|_|get!([$t])).collect::<Vec<_>>()
    };
    ($t: ty) => {
        {
            let mut line = String::new();
            stdin().read_line(&mut line).unwrap();
            line.trim().parse::<$t>().unwrap()
        }
    };
    ($($t: ty),*) => {
        {
            let mut line = String::new();
            stdin().read_line(&mut line).unwrap();
            let mut iter = line.split_whitespace();
            ($(iter.next().unwrap().parse::<$t>().unwrap(),)*)
        }
    };
    ($t: ty; $n: expr) => {
        (0..$n).map(|_|get!($t)).collect::<Vec<_>>()
    };
    ($($t: ty),*; $n: expr) => {
        (0..$n).map(|_|get!($($t),*)).collect::<Vec<_>>()
    };
}

#[allow(unused_macros)]
macro_rules! debug {
    ($($a:expr),*) => {
        #[cfg(debug_assertions)]
        writeln!(&mut std::io::stderr(), concat!("[DEBUG] ", $(stringify!($a), "={:?} "),*), $($a),*).unwrap();
    }
}

const BIG_STACK_SIZE: bool = true;

#[allow(dead_code)]
fn main() {
    use std::thread;
    if BIG_STACK_SIZE {
        thread::Builder::new()
            .stack_size(32 * 1024 * 1024)
            .name("solve".into())
            .spawn(solve)
            .unwrap()
            .join()
            .unwrap();
    } else {
        solve();
    }
}

fn solve() {
    let n = get!(usize);
    let s = get!(String;n)
        .into_iter()
        .map(|e| e.chars().map(|e| e == '1').collect::<Vec<_>>())
        .collect::<Vec<_>>();

    const INF: usize = 1_000_000_000_000_000;
    let mut dist = vec![vec![INF; n]; n];
    let mut nodes = vec![Vec::new(); n];
    for i in 0..n {
        for j in 0..n {
            if s[i][j] {
                dist[i][j] = 1;
                nodes[i].push(j);
            }
            if i == j {
                dist[i][j] = 0;
            }
        }
    }

    let mut queue = VecDeque::new();
    let mut colors = vec![None; n];
    queue.push_back((0, false));
    colors[0] = Some(false);
    while let Some((node, color)) = queue.pop_front() {
        for &next in &nodes[node] {
            if let Some(c) = colors[next] {
                if c == color {
                    println!("-1");
                    return;
                }
            } else {
                queue.push_back((next, !color));
                colors[next] = Some(!color);
            }
        }
    }

    for k in 0..n {
        for i in 0..n {
            for j in 0..n {
                dist[i][j] = min!(dist[i][j], dist[i][k] + dist[k][j]);
            }
        }
    }

    let mut mx = 0;
    for i in 0..n {
        for j in 0..n {
            mx = max!(mx, dist[i][j]);
        }
    }
    println!("{}", mx + 1);
}


Measured memory_bytes: 8572