#include <bits/stdc++.h>
using namespace std;

using vi = vector<int>; using vvi = vector<vi>; using vvvi = vector<vvi>;
using ll = long long int;
using vll = vector<ll>; using vvll = vector<vll>; using vvvll = vector<vvll>;
using vd = vector<double>; using vvd = vector<vd>; using vvvd = vector<vvd>;
using P = pair<int, int>;
using Pll = pair<ll, ll>;
using cdouble = complex<double>;

const double eps = 1e-7;
#define Loop(i, n) for(int i = 0; i < int(n); i++)
#define Loopll(i, n) for(ll i = 0; i < ll(n); i++)
#define Loop1(i, n) for(int i = 1; i <= int(n); i++)
#define Loopll1(i, n) for(ll i = 1; i <= ll(n); i++)
#define Loopr(i, n) for(int i = int(n) - 1; i >= 0; i--)
#define Looprll(i, n) for(ll i = ll(n) - 1; i >= 0; i--)
#define Loopr1(i, n) for(int i = int(n); i >= 1; i--)
#define Looprll1(i, n) for(ll i = ll(n); i >= 1; i--)
#define Foreach(buf, container) for(const auto &buf : container)
#define Loopdiag(i, j, h, w, sum) for(int i = ((sum) >= (h) ? (h) - 1 : (sum)), j = (sum) - i; i >= 0 && j < (w); i--, j++)
#define Loopdiagr(i, j, h, w, sum) for(int j = ((sum) >= (w) ? (w) - 1 : (sum)), i = (sum) - j; j >= 0 && i < (h); j--, i++)
#define Loopdiagsym(i, j, h, w, gap) for (int i = ((gap) >= 0 ? (gap) : 0), j = i - (gap); i < (h) && j < (w); i++, j++)
#define Loopdiagsymr(i, j, h, w, gap) for (int i = ((gap) > (h) - (w) - 1 ? (h) - 1 : (w) - 1 + (gap)), j = i - (gap); i >= 0 && j >= 0; i--, j--)
#define Loopitr(itr, container) for(auto itr = container.begin(); itr != container.end(); itr++)
#define printv(vector) Loop(ex_i, vector.size()) { cout << vector[ex_i] << " "; } cout << endl;
#define printmx(matrix) Loop(ex_i, matrix.size()) { Loop(ex_j, matrix[ex_i].size()) { cout << matrix[ex_i][ex_j] << " "; } cout << endl; }
#define quickio() ios::sync_with_stdio(false); cin.tie(0);
#define bitmanip(m,val) static_cast<bitset<(int)m>>(val)
#define Comp(type_t) bool operator<(const type_t &another) const
#define fst first
#define snd second
#define INF INFINITY
bool feq(double x, double y) { return abs(x - y) <= eps; }
bool inrange(ll x, ll t) { return x >= 0 && x < t; }
bool inrange(vll xs, ll t) { Foreach(x, xs) if (!(x >= 0 && x < t)) return false; return true; }
int ceillog2(ll x) { int ret = 0;	x--; while (x > 0) { ret++; x >>= 1; } return ret; }
ll rndf(double x) { return (ll)(x + (x >= 0 ? 0.5 : -0.5)); }
ll floorsqrt(ll x) { ll m = (ll)sqrt((double)x); return m + (m * m <= x ? 0 : -1); }
ll ceilsqrt(ll x) { ll m = (ll)sqrt((double)x); return m + (x <= m * m ? 0 : 1); }
ll rnddiv(ll a, ll b) { return (a / b + (a % b * 2 >= b ? 1 : 0)); }
ll ceildiv(ll a, ll b) { return (a / b + (a % b == 0 ? 0 : 1)); }
ll gcd(ll m, ll n) { if (n == 0) return m; else return gcd(n, m % n); }
ll lcm(ll m, ll n) { return m * n / gcd(m, n); }

//========================================================================//

class Bipartite_Graph {
private:
	int n;
	vvi sets; // sets[2k] -- sets[2k + 1]
	vi sids;
	bool non_bipartite_flag = false;
public:
	Bipartite_Graph(const vvi &lst) {
		int n = lst.size();
		sids = vi(n, -1);
		Loop(i, n) {
			if (sids[i] == -1) {
				int base = sets.size();
				sets.push_back({});
				sets.push_back({});
				queue<int> que;
				que.push(i);
				sids[i] = base;
				sets[sids[i]].push_back(i);
				while (que.size()) {
					int a = que.front(); que.pop();
					Foreach(b, lst[a]) {
						if (sids[b] == sids[a]) {
							non_bipartite_flag = true;
							return;
						}
						if (sids[b] == -1) {
							sids[b] = sids[a] ^ 1;
							sets[sids[b]].push_back(b);
							que.push(b);
						}
					}
				}
			}
		}
	}
	bool is_bipartite() {
		return !non_bipartite_flag;
	}
	vvi get_sets() {
		return sets;
	}
	vi get_sids() {
		return sids;
	}
};

int main() {
	quickio();
	int n; cin >> n;
	vvi lst(n);
	Loop(i, n) {
		string s; cin >> s;
		Loop(j, n) {
			if (s[j] == '1') {
				lst[i].push_back(j);
			}
		}
	}
	Bipartite_Graph bg(lst);
	if (!bg.is_bipartite()) {
		cout << -1 << endl;
	}
	else {
		vvi sets = bg.get_sets();
		int ans = 0;
		Loop(i, 2) {
			Loop(j, sets[i].size()) {
				int s = sets[i][j];
				queue<int> que;
				vi sids(n, -1);
				sids[s] = 1;
				que.push(s);
				int cnt = 0;
				while (que.size()) {
					int a = que.front(); que.pop();
					Foreach(b, lst[a]) {
						if (sids[b] == -1) {
							sids[b] = sids[a] + 1;
							que.push(b);
							cnt = max(cnt, sids[b]);
						}
					}
				}
				ans = max(ans, cnt);
			}
		}
		cout << ans << endl;
	}
}

Measured memory_bytes: 512