#[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().collect::<Vec<_>>()).collect::<Vec<_>>();

    let mut color = vec![None; n];
    let mut queue = VecDeque::new();
    queue.push_back(0);
    color[0] = Some(false);
    while let Some(node) = queue.pop_front() {
        let c = color[node].unwrap();
        for i in 0..n {
            if s[node][i] == '0' {
                continue;
            }
            if let Some(col) = color[i] {
                if col == c {
                    println!("-1");
                    return;
                }
            } else {
                queue.push_back(i);
                color[i]=Some(!c);
            }
        }
    }

    const INF: usize = 1_000_000_000_000_000;
    let mut dists = vec![vec![INF; n];n];

    for i in 0..n {
        dists[i][i] = 0;
        for j in 0..n {
            if s[i][j] == '1' {
                dists[i][j] = 1;
            }
        }
    }

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

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


Measured memory_bytes: 8572