#define DEBUG 1
#include <algorithm>
#include <cmath>
#include <cstring>
#include <deque>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <string>
#include <tuple>
#include <utility>
#include <vector>
using namespace std;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using vll = vector<ll>;
using vvll = vector<vll>;
using pll = pair<ll, ll>;
using tll = tuple<ll, ll, ll>;
#define all(v) (v).begin(), (v).end()
#define for1(i, n) for (ll i = 0; i < (n); i++)
#define for2(i, m, n) for (ll i = (m); i < (n); i++)
#define for3(i, m, n, d) for (ll i = (m); i < (n); i += (d))
#define rfor2(i, m, n) for (ll i = (m); i > (n); i--)
#define rfor3(i, m, n, d) for (ll i = (m); i > (n); i += (d))
#define INF 1111111111111111111LL
#define MOD 1000000007LL  // 10**9 + 7
#define print(...) print_1(__VA_ARGS__)
#define in(...) in_1(__VA_ARGS__)
#if DEBUG
#define dump(...) dump_1(#__VA_ARGS__, __VA_ARGS__)
#else
#define dump(...)
#endif
template <typename Head>
void dump_1(const char* str, Head&& h)
{
    cerr << str << ": " << h << '\n';
}
template <typename Head, typename... Tail>
void dump_1(const char* str, Head&& h, Tail&&... t)
{
    while (*str != ',') {
        cerr << *str++;
    }
    cerr << ": " << h << ' ';
    dump_1(str + 1, t...);
}
template <typename T1, typename T2>
ostream& operator<<(ostream& os, const pair<T1, T2>& v)
{
    os << '(' << v.first << ", " << v.second << ')';
    return os;
}
template <typename T1, typename T2, typename T3>
ostream& operator<<(ostream& os, const tuple<T1, T2, T3>& v)
{
    os << '(' << get<0>(v) << ", " << get<1>(v) << ", " << get<2>(v) << ')';
    return os;
}
template <typename T>
ostream& operator<<(ostream& os, const vector<T>& v)
{
    for (auto it = v.begin(); it != v.end(); it++) {
        if (it != v.begin()) {
            os << ' ';
        }
        os << *it;
    }
    return os;
}
template <typename T>
ostream& operator<<(ostream& os, const set<T>& v)
{
    for (auto it = v.begin(); it != v.end(); it++) {
        if (it != v.begin()) {
            os << ' ';
        }
        os << *it;
    }
    return os;
}
template <typename T>
ostream& operator<<(ostream& os, const multiset<T>& v)
{
    for (auto it = v.begin(); it != v.end(); it++) {
        if (it != v.begin()) {
            os << ' ';
        }
        os << *it;
    }
    return os;
}
template <typename T1, typename T2>
ostream& operator<<(ostream& os, const map<T1, T2>& v)
{
    os << '{';
    for (auto it = v.begin(); it != v.end(); it++) {
        if (it != v.begin()) {
            os << ", ";
        }
        os << it->first << ':' << it->second;
    }
    os << '}';
    return os;
}
void Yes(void) { cout << "Yes" << '\n'; }
void No(void) { cout << "No" << '\n'; }
void YES(void) { cout << "YES" << '\n'; }
void NO(void) { cout << "NO" << '\n'; }
template <typename T>
void chmax(T& a, const T& b)
{
    if (a < b) {
        a = b;
    }
}
template <typename T>
void chmin(T& a, const T& b)
{
    if (a > b) {
        a = b;
    }
}
template <typename T>
void vin(vector<T>& v, ll len)
{
    for1 (i, len) {
        cin >> v[i];
    }
}
template <typename Head>
void in_1(Head& h)
{
    cin >> h;
}
template <typename Head, typename... Tail>
void in_1(Head& h, Tail&... t)
{
    cin >> h;
    in_1(t...);
}
template <typename Head>
void print_1(Head&& h)
{
    cout << h << '\n';
}
template <typename Head, typename... Tail>
void print_1(Head&& h, Tail&&... t)
{
    cout << h << ' ';
    print_1(t...);
}
//---------------------------------------------------------
vector<string> S(205);
vvll to(205);
ll dis[205][205];
ll color[205];
bool dfs(ll self, ll pos, ll pre, ll cnt, vector<bool>& visited)
{
    // dump(self, pos, pre, cnt);
    if (self == pos && cnt != 0) {
        if (cnt % 2 != 0) {
            return false;
        }
        return true;
    }
    cnt++;
    visited[pos] = true;
    for (ll t : to[pos]) {
        if (t != pre && (t == self || !visited[t])) {
            if (!dfs(self, t, pos, cnt, visited)) {
                return false;
            }
        }
    }
    visited[pos] = false;
    return true;
}
void solve()
{
    ll N;
    in(N);
    for1 (i, N) {
        in(S[i]);
    }
    for1 (i, N) {
        for1 (j, N) {
            if (S[i][j] == '1') {
                to[i].push_back(j);
            }
        }
        // dump(i, to[i]);
    }
    vector<bool> visited(N, false);
    /*
    for1 (i, N) {
        if (!dfs(i, i, -1, 0, visited)) {
            print(-1);
            return;
        }
    }
    */
    queue<pll> q;  // pos,color
    q.push(make_pair(0, 1));
    while (!q.empty()) {
        auto item = q.front();
        q.pop();
        ll pos, col;
        tie(pos, col) = item;
        if (color[pos] == 0) {
            color[pos] = col;
        }
        else if (color[pos] == 1) {
            if (col != 1) {
                print(-1);
                return;
            }
            continue;
        }
        else if (color[pos] == 2) {
            if (col != 2) {
                print(-1);
                return;
            }
            continue;
        }
        col = 3 - col;
        for (ll t : to[pos]) {
            q.push(make_pair(t, col));
        }
    }

    for1 (i, N) {
        for1 (j, N) {
            if (S[i][j] == '1') {
                dis[i][j] = 1;
            }
            else {
                dis[i][j] = INF;
            }
        }
        dis[i][i] = 0;
    }
    for1 (k, N) {
        for1 (i, N) {
            for1 (j, N) {
                if (dis[i][j] > dis[i][k] + dis[k][j]) {
                    dis[i][j] = dis[i][k] + dis[k][j];
                }
            }
        }
    }
    ll ans = 0;
    for1 (i, N) {
        for1 (j, N) {
            if (dis[i][j] < INF) {
                chmax(ans, dis[i][j]);
            }
        }
    }
    print(ans + 1);
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(16);
    cerr << fixed << setprecision(16);
    solve();
}


Measured memory_bytes: 1408