#include <bits/stdc++.h>
#include <random>

using namespace std;

typedef unsigned long long ull;
typedef long long ll;
typedef long double ld;
//#define int ll
//#define int __int128
//#define ll __int128
typedef pair<int, int   > pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<pii> vpi;
typedef vector< vi > vvi;
typedef vector< vvi > vvvi;
typedef vector<short> vs;
typedef vector<vs> vvs;
typedef vector<vvs> vvvs;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<vvl> vvvl;
typedef vector<ld> vld;
typedef vector<vld> vvld;
typedef vector<vvld> vvvld;
typedef vector<string> vst;
typedef vector<vst> vvst;
typedef pair<ld, ld> pld;
//typedef complex<double> base;

#define inmin(a, b) a = min(a, (b))
#define inmax(a, b) a = max(a, (b))
#define ALL(a) a.begin(),a.end()
#define RALL(a) a.rbegin(),a.rend()
#define sqr(x) ((x) * (x))
#define sqr3(x) ((x) * (x) * (x))
#define fori(i, n) for(int i = 0; i < (int)(n); ++i)
#define SZ(a) ((int)((a).size()))
#define triple(T) tuple<T, T, T>
#define quad(T) tuple<T, T, T, T>
#define watch(x) cerr << (#x) << " = " << (x) << endl;
#define mp(a, b) make_pair(a, b)

#ifdef MAX_HOME
#define cerr cout
#else
#define cerr if (false) cerr
#endif

const double PI = 2 * acos(0.0);
#define rand shittttty_shit
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
mt19937_64 rng_64(chrono::steady_clock::now().time_since_epoch().count());

const string DIGITS = "0123456789";
const string ALPH = "abcdefghijklmnopqrstuvwxyz";

template <class T0, class T1>
inline ostream & operator << (ostream &out, pair<T0, T1> &a) {
    return out << "{" << a.first << ", " << a.second << "}";
}

template <class T0, class T1, class T2>
inline ostream & operator << (ostream &out, tuple<T0, T1, T2> &a) {
    return out << "{" << get<0>(a) << ", " << get<1>(a) << ", " << get<2>(a) << "}";
}

template <class T0, class T1, class T2, class T3>
inline ostream & operator << (ostream &out, tuple<T0, T1, T2, T3> &a) {
    return out << "{" << get<0>(a) << ", " << get<1>(a) << ", " << get<2>(a) << ", " <<  get<3>(a) << "}";
}

template<class T>
inline ostream & operator << (ostream &out, vector<T> &a) {
    out << "[";
    fori (i, a.size())
        out << a[i] << vector<string>{", ", "]  "}[i + 1 == a.size()];
    return out;
}

ostream & operator << (ostream &out, pii a) {
    cout << a.first << " " << a.second ;
    return out;
}

void smain();

signed main() {

#ifdef MAX_HOME
    freopen("input.txt", "r", stdin);
    clock_t start = clock();
#endif
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    cout << setprecision(12) << fixed;
    smain();
#ifdef MAX_HOME
    cout << "\n\n\n\nTOTAL EXECUTION TIME: " << float( clock () - start ) /  CLOCKS_PER_SEC << endl;
#endif
    return 0;
}

const int N = 222;

string g[N];
int n;

int color[N];
bool wrong = false;
void dfs(int v) {
    fori (to, n) if (g[v][to] == '1') {
        if (color[to]) {
            if (color[to] == color[v]) wrong = true;

        } else {
            color[to] = 1;
            if (color[v] == 1)
                color[to] = 2;
            dfs(to);
        }
    }
}

int q[N + N];

int dij(int s) {
    vi d(n, -1);
    int ql, qr;
    ql = qr = 0;
    q[qr++] = s;
    d[s] = 0;
    while (ql < qr) {
        int v = q[ql++];
        for (int to = 0; to < n; ++to) {
            if (g[v][to] == '1') {
                if (d[to] == -1) {
                    d[to] = d[v] + 1;
                    q[qr++] = to;
                }
            }
        }
    }
    return *max_element(ALL(d)) + 1;
}

void smain() {

    cin >> n;
    fori (i, n) {
        cin >> g[i];
    }

    fori (i, n) {
        if (color[i])
            continue;
        color[i] = 1;
        dfs(i);
    }

    if (wrong) {
        cout << "-1";
        return;
    }
    int ans = 0;
    fori (i, n) {
        int cur = dij(i);
        inmax(ans, cur);
    }
    cout << ans;
}

Measured memory_bytes: 384