// May this submission get accepted!

#pragma GCC optimize ("O3")
#pragma GCC target ("tune=native")
#pragma GCC target ("avx")

#include <bits/stdc++.h>

// 汎用マクロ
#define ALL_OF(x) (x).begin(), (x).end()
#define REP(i,n) for (long long i=0, i##_len=(n); i<i##_len; i++)
#define RANGE(i,is,ie) for (long long i=(is), i##_end=(ie); i<=i##_end; i++)
#define DSRNG(i,is,ie) for (long long i=(is), i##_end=(ie); i>=i##_end; i--)
#define STEP(i, is, ie, step) for (long long i=(is), i##_end=(ie), i##_step = (step); i<=i##_end; i+=i##_step)
#define UNIQUE(v) do { sort((v).begin(), (v).end()); (v).erase(unique((v).begin(), (v).end()), (v).end()); } while (false)
template<class T> bool chmax(T &a, const T &b) {if (a < b) {a = b; return true;} return false; }
template<class T> bool chmin(T &a, const T &b) {if (a > b) {a = b; return true;} return false; }
#define INF 0x7FFFFFFF
#define LINF 0x7FFFFFFFFFFFFFFFLL
#define Yes(q) ((q) ? "Yes" : "No")
#define YES(q) ((q) ? "YES" : "NO")
#define Possible(q) ((q) ? "Possible" : "Impossible")
#define POSSIBLE(q) ((q) ? "POSSIBLE" : "IMPOSSIBLE")
#define DUMP(q) cerr << "[DEBUG] " #q ": " << (q) << " at " __FILE__ ":" << __LINE__ << endl
#define DUMPALL(q) do { cerr << "[DEBUG] " #q ": ["; REP(i, (q).size()) { cerr << (q)[i] << (i == i_len-1 ? "" : ", "); } cerr << "] at " __FILE__ ":" << __LINE__ << endl; } while (false)
template<class T> T gcd(T a, T b) { if (a < b) swap(a, b); while (b) swap(a %= b, b); return a; }
template<class T> T lcm(const T a, const T b) { return a / gcd(a, b) * b; }

// gcc拡張マクロ
#define popcount __builtin_popcount
#define popcountll __builtin_popcountll

// エイリアス
#define DANCE_ long
#define ROBOT_ unsigned
#define HUMAN_ signed
#define CHOKUDAI_ const
using  ll = DANCE_ HUMAN_ DANCE_;
using ull = DANCE_ ROBOT_ DANCE_;
using cll = DANCE_ DANCE_ CHOKUDAI_;
using  ld = long double;
using namespace std;

// モジュール

// 二部グラフか判定 O(|E|)
bool is_bigraph(const vector<vector<ll>> &g) {
    ll n = g.size();
    vector<ll> color(n, -1);
    deque<ll> q = {0};
    color[0] = 0;
    while (q.size()) {
        ll u = q.back(); q.pop_back();
        for (ll v : g[u]) {
            if (color[v] == -1) {
                color[v] = !color[u];
                q.push_back(v);
            } else if (color[u] == color[v]) {
                return false;
            }
        }
    }
    return true;
}

// 処理内容
int main() {
    
    // インタラクティブ問題では除去した方がいいかも
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    

    // |E| = O(N^2), |V| = N
    ll n; cin >> n;
    vector<string> s(n);
    REP(i, n) cin >> s[i];

    vector<vector<ll>> g(n);
    REP(i, n) REP(j, n) {
        if (s[i][j] == '1') {
            g[i].push_back(j);
        }
    }
    REP(i, n) {
        sort(ALL_OF(g[i]));
    }

    if (!is_bigraph(g)) {
        cout << -1 << endl;
        return 0;
    }

    ll ans = 0;
    REP(i, n) {
        vector<ll> dst(n, -1);
        deque<ll> q = {i};
        dst[i] = 1;
        while (q.size()) {
            ll u = q.front(); q.pop_front();
            for (ll v : g[u]) {
                if (dst[v] == -1) {
                    dst[v] = dst[u] + 1;
                    q.push_back(v);
                }
            }
        }
        chmax(ans, *max_element(ALL_OF(dst)));
    }
    cout << ans << endl;
    
}

Measured memory_bytes: 768