#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using VI = vector<ll>;
using VV = vector<VI>;
using VS = vector<string>;

// tourist set
template <typename A, typename B>
string to_string(pair<A, B> p);

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p);

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);

string to_string(const string& s) {
  return '"' + s + '"';
}

string to_string(const char* s) {
  return to_string((string) s);
}

string to_string(bool b) {
  return (b ? "true" : "false");
}

string to_string(vector<bool> v) {
  bool first = true;
  string res = "{";
  for (int i = 0; i < static_cast<int>(v.size()); i++) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(v[i]);
  }
  res += "}";
  return res;
}

template <size_t N>
string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++) {
    res += static_cast<char>('0' + v[i]);
  }
  return res;
}

template <typename A>
string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}

template <typename A, typename B>
string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ")";
}

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")";
}

void debug_out() { cerr << endl; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}

#ifdef LOCAL
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif
// tourist set end

template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }

#define FOR(i,a,b) for(ll i=(a);i<(b);++i)
#define rep(i,b) FOR(i, 0, b)
#define ALL(v) (v).begin(), (v).end()
#define p(s) cout<<(s)<<endl
#define p2(s, t) cout << (s) << " " << (t) << endl
#define br() p("")
#define pn(s) cout << (#s) << " " << (s) << endl
#define p_yes() p("YES")
#define p_no() p("NO")
#define SZ(x) ((int)(x).size())

void no(){p_no(); exit(0);}
void yes(){p_yes(); exit(0);}

const ll mod = 1e9 + 7;
const ll inf = 1e18;

void vprint(vector<ll> A){
    ll L = A.size();
    FOR(i, 0, L){
        if(i) cout << ' ';
        cout << A[i];
    }
    cout << endl;
}

ll N; 
VS M;
VV G;

bool is_connected(ll i, ll j){
  if(M[i][j]=='1'){
    return true;
  }else{
    return false;
  }
}

ll set_connected(set<ll> se){
  VI V;
  for(ll i : se){
    V.push_back(i);
  }
  debug(V);
  rep(i, V.size()){
    rep(j, V.size()){
      if(is_connected(V[i], V[j])){
        return true;
      }
    }
  }
  return false;
}

vector<bool> visited;

set<ll> get_next(set<ll> se){
  set<ll> next;
  for(ll i : se){
    for(ll to : G[i]){
      if(!visited[to]){
        next.insert(to);
        visited[to] = true;
      }
    }
  }
  return next;
}

// s : 始点
ll f(ll start){
  visited.resize(N, false);
  rep(i, N){
    visited[i] = false;
  }
  debug(visited);
  set<ll> se;
  se.insert(start);
  visited[start] = true;
  debug(start);

  ll k = 1;
  while(true){
    debug(se);
    auto next = get_next(se);
    debug(next);

    if(next.size()==0) break;

    if(set_connected(next)){
      debug("connected..");
      return -1;
    }

    k++;
    se = next;
  }
  return k;
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    // input
    cin >> N;

    M.resize(N);
    G.resize(N);
    rep(i, N){
      string s; cin >> s;
      M[i] = s;
      rep(j, N){
        if(s[j]=='1'){
          G[i].push_back(j);
        }
      }
    }
    
    ll ma = -1;
    rep(i, N){
      ll k = f(i);
      debug("f", i, k);
      debug("-------end-------");
      chmax(ma, k);
    }

    p(ma);

    return 0;
}

Measured memory_bytes: 768