/**
 * 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;

#ifndef DEFINE_WARSHALLFLOYD_HPP
#define DEFINE_WARSHALLFLOYD_HPP


using namespace std;

namespace warshall {

    using ll = long long;
    const ll inf = 1e18;

    class WarshallFloyd {
    public:
        int n;
        vector<vector<ll>> g;

        WarshallFloyd(int n);
        void add(int from, int to, ll cost);
        void build();
        ll result(int from, int to);
    };

    WarshallFloyd::WarshallFloyd(int n) : n(n) {
        g.assign(n, vector<ll>(n, inf));
        for (int i = 0; i < n; i++) {
            g[i][i] = 0;
        }
    }

    void WarshallFloyd::add(int from, int to, ll cost) {
        g[from][to] = cost;
    }

    void WarshallFloyd::build() {
        for (int k = 0; k < n; k++) {
            for (int i = 0; i < n; i++) {
                for (int j = 0; j < n; j++) {
                    if(g[i][k] == inf || g[k][j] == inf) continue;
                    g[i][j] = min(g[i][j], g[i][k] + g[k][j]);
                }
            }
        }
    }

    ll WarshallFloyd::result(int from, int to) {
        return g[from][to];
    }

}

// verify
// https://atcoder.jp/contests/abc012/tasks/abc012_4

#endif //DEFINE_WARSHALLFLOYD_HPP
using warshall::WarshallFloyd;

#ifndef DEFINE_UNIONFIND_HPP
#define DEFINE_UNIONFIND_HPP


#include <numeric>

using namespace std;

namespace unionfind {

    using ll = long long;

    class UnionFind {
    public:
        ll n;
        vector<ll> par;
        vector<ll> rank;
        vector<ll> size;

        UnionFind(int n);
        ll find(ll x);
        void unite(ll x, ll y);
        bool same(ll x, ll y);
        ll getsize(ll x);
        int rootCount();
    };

    UnionFind::UnionFind(int n):n(n), par(n, 0), rank(n, 0), size(n, 1) {
        iota(par.begin(), par.end(), 0);
    }

    ll UnionFind::find(ll x) {
        if (par[x] == x) return x;
        else return par[x] = find(par[x]);
    }

    void UnionFind::unite(ll x, ll y) {
        x = find(x);
        y = find(y);
        if (x == y) return;
        if (rank[x] < rank[y]) {
            par[x] = y;
            size[y] += size[x];
        } else {
            par[y] = x;
            size[x] += size[y];
            if (rank[x] == rank[y]) rank[x]++;
        }
    }

    bool UnionFind::same(ll x, ll y) {
        return find(x) == find(y);
    }

// get size of tree
    ll UnionFind::getsize(ll x) {
        return size[find(x)];
    }

// get the number of roots
    int UnionFind::rootCount() {
        int cnt = 0;
        for (int i = 0; i < n; i++) {
            if (i == par[i]) cnt++;
        }
        return cnt;
    }


// verify
// https://atc001.contest.atcoder.jp/tasks/unionfind_a

}

#endif //DEFINE_UNIONFIND_HPP
using unionfind::UnionFind;

int g[205][205];

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

        UnionFind uf(2*n);
        WarshallFloyd wf(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';
                if(g[i][j]){
                    wf.add(i, j, 1LL);
                    wf.add(j, i, 1LL);
                    uf.unite(i, j+n);
                    uf.unite(i+n, j);
                }
            }
        }

        bool flg = true;
        for(int i=0; i<n; i++){
            if(uf.same(i, i+n)) flg = false;
        }

        if(!flg) {
            out << -1 << endl;
            return;
        }

        ll mx = 0;
        wf.build();
        for(int i=0; i<n; i++){
            for(int j=0; j<n; j++){
                if(wf.result(i, j) != 1e18) chmax(mx, wf.result(i, j));
            }
        }

        out << mx+1 << endl;
	}
};


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


Measured memory_bytes: 768