/**
 * code generated by JHelper
 * More info: https://github.com/AlexeyDmitriev/JHelper
 * @author champon
 */

#include <iostream>
#include <fstream>

#include <bits/stdc++.h>
#define se cout << "test ok" << endl;
#define sp << " " <<
using namespace std;
using ll = long long;
using ld = long double;
ll mod = ll(1e9)+7;
ll inf = ll(5e18);
template<typename T1, typename T2> ll ceill(T1 a, T2 b){ return (a+b-1)/b; }
void ans(bool b, ostream& out=cout){ out << (b ? "Yes" : "No") << endl; }
void ans2(bool b, ostream& out=cout){ out << (b ? "YES" : "NO") << endl; }
template<typename T> inline bool chmax(T &a, T b){ if(a<b){a=b; return true;} return false; }
template<typename T> inline bool chmin(T &a, T b){ if(a>b){a=b; return true;} return false; }
template<typename A, size_t N, typename T> void Fill(A (&array)[N], const T &val){ fill((T*)array, (T*)(array+N), val); }
int dx[] = {1, 0, -1, 0, 1, -1, 1, -1};
int dy[] = {0, 1, 0, -1, 1, -1, -1, 1};

#ifndef INCLUDE_DEBUG_HPP
#define INCLUDE_DEBUG_HPP

#include <iostream>
#include <vector>
#include <map>
using namespace std;

namespace dbg {
    using ll = long long;

    class Debug {
    public:
        Debug(){}
        template<typename T>
        void vd(vector<T> vec);
        template<typename T>
        void vd2(vector<vector<T>> vec);
        template<typename T>
        void ad(T *arr, ll n);
        template<typename T, size_t N>
        void ad2(T (&arr)[N], ll n);
        template<typename T>
        void md(T mp);
    };

    template<typename T>
    void Debug::vd(vector<T> vec) {
        for (auto vv : vec) cout << vv << " ";
        cout << endl;
    }

    template<typename T>
    void Debug::vd2(vector<vector<T>> vec) {
        for (auto vv : vec) for (auto vvv : vv) cout << vvv << " ";
        cout << endl;
    }

    template<typename T>
    void Debug::ad(T *arr, ll n) {
        for (int i = 0; i <= n; i++) cout << arr[i] << " ";
        cout << endl;
    }

    template<typename T, size_t N>
    void Debug::ad2(T (&arr)[N], ll n) {
        for (int i = 0; i <= N; i++) for (int j = 0; j <= n; j++) cout << arr[i][j] << " ";
        cout << endl;
    }

    template<typename T>
    void Debug::md(T mp) {
        cout << "key : value" << endl;
        for (auto const &m : mp) cout << m.first << " : " << m.second << endl;
        cout << endl;
    }

}

#endif //INCLUDE_DEBUG_HPP

using dbg::Debug;
Debug debug;

int g[205][205];

class BGraphPartition {
public:
	void solve(std::istream& in, std::ostream& out) {
        int n;
        string s;
        in >> n;

        for(int i=0; i<n; i++){
            in >> s;
            for(int j=0; j<n; j++){
                g[i][j] = s[j]-'0';
                g[j][i] = s[j]-'0';
            }
        }

        bool res = false;
        int mx = 0;
        for(int i=0; i<n; i++){
            queue<int> que;
            vector<int> v(n, 0);
            vector<int> visited(n, 0);
            que.push(i);
            visited[i] = 1;
            while(!que.empty()){
                int u = que.front(); que.pop();
                for(int j=0; j<n; j++){
                    if(visited[j]) continue;
                    if(g[u][j]) {
                        visited[j] = 1;
                        v[j] = v[u]+1;
                        que.push(j);
                    }
                }
            }

            bool flg = true;
            for(int j=0; j<n; j++){
                for(int k=0; k<n; k++){
                    if(g[j][k] && v[j] != v[k]+1 && v[k] != v[j]+1){
                        flg = false;
                        break;
                    }
                }
                if(!flg) break;
            }

            if(!flg) continue;

            res = true;
            set<int> sv;
            for(int j=0; j<n; j++){
                sv.insert(v[j]);
            }
            chmax(mx, int(sv.size()));
        }

        if(!res) out << -1 << endl;
        else out << mx << endl;
	}
};


int main() {
	BGraphPartition solver;
	std::istream& in(std::cin);
	std::ostream& out(std::cout);
	solver.solve(in, out);
	return 0;
}


Measured memory_bytes: 384