#define DEBUG 0
/**
 * File    : B.cpp
 * Author  : Kazune Takahashi
 * Created : 2019/10/13 18:49:50
 * Powered by Visual Studio Code
 */
#include <iostream>
#include <iomanip>
#include <algorithm>
#include <vector>
#include <string>
#include <complex>
#include <tuple>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <unordered_map>
#include <unordered_set>
#include <bitset>
#include <functional>
#include <random>
#include <chrono>
#include <cctype>
#include <cassert>
#include <cmath>
#include <cstdio>
#include <cstdlib>
using namespace std;
template <typename T>
void ch_max(T &left, T right)
{
  if (left < right)
  {
    left = right;
  }
}
template <typename T>
void ch_min(T &left, T right)
{
  if (left > right)
  {
    left = right;
  }
}
using ll = long long;
class mint
{
public:
  static ll MOD;
  ll x;
  mint() : x(0) {}
  mint(ll x) : x(x % MOD) {}
  mint operator-() const { return x ? MOD - x : 0; }
  mint &operator+=(const mint &a)
  {
    if ((x += a.x) >= MOD)
    {
      x -= MOD;
    }
    return *this;
  }
  mint &operator-=(const mint &a) { return *this += -a; }
  mint &operator*=(const mint &a)
  {
    (x *= a.x) %= MOD;
    return *this;
  }
  mint &operator/=(const mint &a)
  {
    mint b{a};
    return *this *= b.power(MOD - 2);
  }
  mint operator+(const mint &a) const { return mint(*this) += a; }
  mint operator-(const mint &a) const { return mint(*this) -= a; }
  mint operator*(const mint &a) const { return mint(*this) *= a; }
  mint operator/(const mint &a) const { return mint(*this) /= a; }
  bool operator<(const mint &a) const { return x < a.x; }
  bool operator==(const mint &a) const { return x == a.x; }
  const mint power(ll N)
  {
    if (N == 0)
    {
      return 1;
    }
    else if (N % 2 == 1)
    {
      return *this * power(N - 1);
    }
    else
    {
      mint half = power(N / 2);
      return half * half;
    }
  }
};
ll mint::MOD = 1e9 + 7;
istream &operator>>(istream &stream, mint &a) { return stream >> a.x; }
ostream &operator<<(ostream &stream, const mint &a) { return stream << a.x; }
class combination
{
public:
  vector<mint> inv, fact, factinv;
  static int MAX_SIZE;
  combination() : inv(MAX_SIZE), fact(MAX_SIZE), factinv(MAX_SIZE)
  {
    inv[1] = 1;
    for (auto i = 2; i < MAX_SIZE; i++)
    {
      inv[i] = (-inv[mint::MOD % i]) * (mint::MOD / i);
    }
    fact[0] = factinv[0] = 1;
    for (auto i = 1; i < MAX_SIZE; i++)
    {
      fact[i] = mint(i) * fact[i - 1];
      factinv[i] = inv[i] * factinv[i - 1];
    }
  }
  mint operator()(int n, int k)
  {
    if (n >= 0 && k >= 0 && n - k >= 0)
    {
      return fact[n] * factinv[k] * factinv[n - k];
    }
    return 0;
  }
};
int combination::MAX_SIZE = 3000010;
ll gcd(ll x, ll y) { return y ? gcd(y, x % y) : x; }
// constexpr double epsilon = 1e-10;
constexpr ll infty = 1e9 + 7;
// constexpr int dx[4] = {1, 0, -1, 0};
// constexpr int dy[4] = {0, 1, 0, -1};
void Yes()
{
  cout << "Yes" << endl;
  exit(0);
}
void No()
{
  cout << "-1" << endl;
  exit(0);
}

int calc_diam(vector<vector<int>> &V)
{
  int N = V.size();
  for (auto k = 0; k < N; k++)
  {
    for (auto i = 0; i < N; i++)
    {
      for (auto j = 0; j < N; j++)
      {
        ch_min(V[i][j], V[i][k] + V[k][j]);
      }
    }
  }
  int diam{0};
  for (auto i = 0; i < N; i++)
  {
    for (auto j = 0; j < N; j++)
    {
      ch_max(diam, V[i][j]);
    }
  }
  return diam;
}

bool bipartite(vector<vector<int>> const &V)
{
  int N = V.size();
  vector<int> color(N, -1);
  using info = tuple<int, int>;
  stack<info> S;
  S.push(info(0, 0));
  while (!S.empty())
  {
    int now, col;
    tie(now, col) = S.top();
    S.pop();
    if (color[now] == -1)
    {
      color[now] = col;
      for (auto i = 0; i < N; i++)
      {
        if (i != now && V[now][i] == 1 && color[i] == -1)
        {
          S.push(info(i, 1 - col));
        }
      }
    }
    else if (color[now] != col)
    {
      No();
    }
  }
  return true;
}

int main()
{
  int N;
  cin >> N;
  vector<vector<int>> V(N, vector<int>(N, infty));
  for (auto i = 0; i < N; i++)
  {
    string S;
    cin >> S;
    for (auto j = 0; j < N; j++)
    {
      if (S[j] == '1')
      {
        V[i][j] = 1;
      }
      else if (i == j)
      {
        V[i][j] = 0;
      }
    }
  }
  if (bipartite(V))
  {
    int diam{calc_diam(V)};
    cout << diam + 1 << endl;
  }
}

Measured memory_bytes: 512