// Marcin Knapik
#include<bits/stdc++.h>
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")

using namespace std;

// #include <ext/pb_ds/assoc_container.hpp> // order_of_key
// #include <ext/pb_ds/tree_policy.hpp> // find by order
// using namespace __gnu_pbds; 
// #define ordered_set tree< int , null_type,less< int >, rb_tree_tag,tree_order_statistics_node_update>  

// const ll MAX_LL = 0xFFFFFFFFFFFFFFFF;
// mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
// #define losuj(a, b) uniform_int_distribution<ull>(a, b)(rng)

typedef long double             ld;
typedef long long               ll;
typedef pair<int, int>          ii;
typedef vector<int>             vi;
typedef vector<vi>              vvi;

#define sz(a)                   (int)(a).size()
#define pb                      push_back
#define all(c)                  (c).begin(), (c).end()
#define FOR(i, a)               for (int i = 0; i < (a); i++)
#define f                       first
#define s                       second

template <class T> inline bool setmin(T &a, T b){if (a > b)return a = b, 1;return 0;}
template <class T> inline bool setmax(T &a, T b){if (a < b)return a = b, 1;return 0;}

template<class T> inline T fast(T a,T b,T mod) {ll res = 1; while(b){if(b&1) res = (res*a)%mod;a = (a*a)%mod;b >>= 1;}return res;}
template<class T> istream &operator>>(istream &os, vector<T> &container){for (auto &u : container)os >> u;return os;}
template<class T> ostream &operator<<(ostream &os, const vector<T> &container){for (auto &u : container)os << u << " ";return os;}
template<class T> inline T gcd(T a, T b) { while (b)swap(a %= b, b); return a; }

const ll INF = 1e9 + 7;
const ll mod = 998244353;
const ll BIG_INF = 1e18+7;
const ll N = 1e6+7;
const ll T = 1<<20;

const ld eps = 1e-12;

ll n, m, k, q;

vvi G(N);
int kolor[N];
bitset<201> odw;

vi teraz;
vvi pom;

void dfs1(int v){
    odw[v] = 1;
    teraz.pb(v);

    for(auto & u : G[v]){
        if(!odw[u]){
            kolor[u] = (kolor[v] + 1) & 1;
            dfs1(u);
        }
        else if(kolor[u] == kolor[v]){
            cout << -1 << '\n';
            exit(0);
        }
    }
}
int odl[N];

int bfs(int x){
    odw.reset();
    queue<int> kol;
    odl[x] = 1;
    odw[x] = 1;
    int last = x;
    kol.push(x);

    while(sz(kol)){
        int v = kol.front();
        kol.pop();
        last = v;

        for(auto & u : G[v]){
            if(!odw[u]){
                odw[u] = 1;
                odl[u] = odl[v] + 1;
                kol.push(u);
            }
        }
    }
    return odl[last];
}

int policz(vi&temp){
    int ret = 0;
    for(auto & u : temp)
        ret = max(ret, bfs(u));
    return ret;
} 

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

    cin >> n;

    for(int i = 1; i <= n; i++){
        for(int j = 1; j <= n; j++){
            char temp;
            cin >> temp;

            if(temp == '1')
                G[i].pb(j);
        }
    }


    for(int i = 1; i <= n; i++)
        if(!odw[i]){
            dfs1(i);
            pom.pb(teraz);
            teraz.clear();
        }
    
    int ans = 0;
    for(auto & u : pom){
        ans += policz(u);
    }
    cout << ans << '\n';
}   

Measured memory_bytes: 25984