#include <bits/stdc++.h>
using namespace std;
using lint = long long;
const lint mod = 1e9 + 7;
#define all(x) (x).begin(), (x).end()
#define bitcount(n) __builtin_popcountl((lint)(n))
#define fcout cout << fixed << setprecision(15)
#define highest(x) (63 - __builtin_clzl(x))
template<class T> inline void YES(T condition){ if(condition) cout << "YES" << endl; else cout << "NO" << endl; }
template<class T> inline void Yes(T condition){ if(condition) cout << "Yes" << endl; else cout << "No" << endl; }
template<class T = string, class U = char>int character_count(T text, U character){ int ans = 0; for(U i: text){ ans += (i == character); } return ans; }
lint power(lint base, lint exponent, lint module){ if(exponent % 2){ return power(base, exponent - 1, module) * base % module; }else if(exponent){ lint root_ans = power(base, exponent / 2, module); return root_ans * root_ans % module; }else{ return 1; }}
struct position{ int y, x; }; position mv[4] = {{0, -1}, {1, 0}, {0, 1}, {-1, 0}}; // double euclidean(position first, position second){ return sqrt((second.x - first.x) * (second.x - first.x) + (second.y - first.y) * (second.y - first.y)); }
template<class T, class U> string to_string(pair<T, U> x){ return to_string(x.first) + "," + to_string(x.second); } string to_string(string x){ return x; }
template<class itr> void array_output(itr start, itr goal){ string ans; for(auto i = start; i != goal; i++) ans += to_string(*i) + " "; if(!ans.empty()) ans.pop_back(); cout << ans << endl; }
template<class itr> void cins(itr first, itr last){ for(auto i = first; i != last; i++){ cin >> (*i); } }
template<class T> T gcd(T a, T b){ if(a && b){ return gcd(min(a, b), max(a, b) % min(a, b)); }else{ return a; }} template<class T> T lcm(T a, T b){ return a / gcd(a, b) * b; }
struct combination{ vector<lint> fact, inv; combination(int sz) : fact(sz + 1), inv(sz + 1){ fact[0] = 1; for(int i = 1; i <= sz; i++){ fact[i] = fact[i - 1] * i % mod; } inv[sz] = power(fact[sz], mod - 2, mod); for(int i = sz - 1; i >= 0; i--){ inv[i] = inv[i + 1] * (i + 1) % mod; } } lint C(int p, int q) const{ if(q < 0 || p < q) return 0; return (fact[p] * inv[q] % mod * inv[p - q] % mod); } };
template<class itr> bool next_sequence(itr first, itr last, int max_bound){ itr now = last; while(now != first){ now--; (*now)++; if((*now) == max_bound){ (*now) = 0; }else{ return true; } } return false; }

struct UnionFind {
    vector< int > data;
    
    UnionFind(int sz) {
        data.assign(sz, -1);
    }
    
    bool unite(int x, int y) {
        x = find(x), y = find(y);
        if(x == y) return (false);
        if(data[x] > data[y]) swap(x, y);
        data[x] += data[y];
        data[y] = x;
        return (true);
    }
    
    int find(int k) {
        if(data[k] < 0) return (k);
        return (data[k] = find(data[k]));
    }
    
    int size(int k) {
        return (-data[find(k)]);
    }
};

struct BipartiteGraph : UnionFind
{
    vector< int > color;
    
    BipartiteGraph(int v) : color(v + v, -1), UnionFind(v + v) {}
    
    bool bipartite_graph_coloring()
    {
        for(int i = 0; i < color.size() / 2; i++) {
            int a = find(i);
            int b = find(i + (int) color.size() / 2);
            if(a == b) return (false);
            if(color[a] < 0) color[a] = 0, color[b] = 1;
        }
        return (true);
    }
    
    bool operator[](int k)
    {
        return (bool(color[find(k)]));
    }
};

int main(){
    int N;
    cin >> N;
    int dist[N][N];
    BipartiteGraph graph(N);
    for(int i = 0; i < N; i++){
        for(int j = 0; j < N; j++){
            char x;
            cin >> x;
            if(x == '1'){
                dist[i][j] = 1;
                graph.unite(i, j + N);
                graph.unite(i + N, j);
            }else{
                dist[i][j] = 1e9;
            }
            if(i == j){
                dist[i][j] = 0;
            }
        }
    }
    if(!graph.bipartite_graph_coloring()){
        cout << -1 << endl;
        return 0;
    }
    for(int i = 0; i < N; i++){
        for(int j = 0; j < N; j++){
            for(int k = 0; k < N; k++){
                dist[j][k] = min(dist[j][k], dist[j][i] + dist[i][k]);
            }
        }
    }
    int ans = 0;
    for(int i = 0; i < N; i++){
        for(int j = 0; j < N; j++){
            ans = max(ans, dist[i][j]);
        }
    }
    cout << ans + 1 << endl;
}


Measured memory_bytes: 384