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

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

#define set0(x) memset(x,0,sizeof(x))
#define F first
#define S second
#define PB push_back
#define MP make_pair
#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define trav(a, x) for(auto& a : x)
#define all(x) x.begin(), x.end()
#define sz(x) (int)(x).size()

typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
template<typename T> void read(T &x){
    x = 0;char ch = getchar();ll f = 1;
    while(!isdigit(ch)){if(ch == '-')f*=-1;ch=getchar();}
    while(isdigit(ch)){x = x*10+ch-48;ch=getchar();}x*=f;
}
template<typename T, typename... Args> void read(T &first, Args& ... args) {
    read(first);
    read(args...);
}

int n,vis[220],dis[220];
char S[220][220];
vector<int> G[220];
int main() {
    read(n);
    for(int i=1;i<=n;i++){
        cin>>(S[i]+1);
        for(int j=1;j<=n;j++)if(S[i][j] == '1')G[i].PB(j);
    }
    int ans = 0;
    for(int i=1;i<=n;i++){
        if(!vis[i]){
            vector<int> V;
            V.PB(i);
            set0(dis);
            dis[i] = 1;
            for(int p = 0;p<V.size();p++){
                vis[V[p]] = 1;
                trav(ct,G[V[p]]){
                    if(!dis[ct]){
                        V.PB(ct);
                        dis[ct] = dis[V[p]]+1;
                    }else{
                        if(abs(dis[ct]-dis[V[p]])!=1){
                            cout<<-1<<endl;
                            exit(0);
                        }
                    }
                }
            }
            int cans = 0;
            trav(ech,V){
                set0(dis);
                vector<int> V2;
                V2.PB(ech);
                dis[ech] = 1;
                for(int p = 0;p<V2.size();p++){
                    cans = max(cans,dis[V2[p]]);
                    trav(ct,G[V2[p]]){
                        if(!dis[ct]){
                            V2.PB(ct);dis[ct] = dis[V2[p]]+1;
                        }
                    }
                }
            }
            ans+=cans;
        }
    }
    cout<<ans<<endl;
    return 0;
}


Measured memory_bytes: 512