#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;

template <typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template <typename T>
using dijkstra = priority_queue<T, vector<T>, greater<T>>;

using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define fbo find_by_order // k th index
#define ook order_of_key // strictly smaller than k
#define PI acos(-1.0)
#define inf 0x3f3f3f3f
#define max_ull 18446744073709551615
#define max_ll 9223372036854775807
#define lead_zero(x) __builtin_clzll(x)
#define trail_zero(x) __builtin_ctzll(x)
#define total_1s(x) __builtin_popcountll(x)
#define first_1(x) __builtin_ffsll(x)
#define log2_(x) __builtin_clz(1) - __builtin_clz(x)
#define isLeap(x) ((x % 400 == 0) || (x % 100 ? x % 4 == 0 : false))
#define QUERY           \
    int test;           \
    scanf("%d", &test); \
    for (int _T = 1; _T <= test; _T++)
#define FAST ios_base::sync_with_stdio(0), cin.tie(0)
#define all(v) v.begin(), v.end()
#define reunique(v) v.resize(std::unique(all(v)) - v.begin())
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pul pair<ull,ull>
#define ff first
#define ss second
#define MERGE(v1, v2, v) merge(all(v1), all(v2), back_inserter(v))
#define MP make_pair
#define EB emplace_back
#define read freopen("input.txt", "r", stdin)
#define write freopen("output.txt", "w", stdout)
#define in_range(v, r, l) upper_bound(all(v), r) - lower_bound(all(v), l)
#define LCM(a, b) (a / __gcd(a, b)) * b;
#define SEGMENT_TREE int mid=(st+en)/2,lt=node*2,rg=lt+1
template <typename T1, typename T2>
ostream& operator<<(ostream& fout, const pair<T1, T2>& ps) {
    fout << ps.ff << " " << ps.ss;
    return fout;
}
template <typename T1, typename T2>
ostream& operator<<(ostream& fout, const map<T1, T2>& mp) {
    for (pair<T1, T2> i : mp)
        fout << i.first << " : " << i.second << "\n";
    return fout;
}
template <typename T>
ostream& operator<<(ostream& fout, const vector<T>& v) {
    for (T i : v)
        fout << i << " ";
    return fout;
}
template <typename T>
ostream& operator<<(ostream& fout, const set<T>& v) {
    for (T i : v)
        fout << i << " ";
    return fout;
}
template <typename T>
ostream& operator<<(ostream& fout, const ordered_set<T>& v) {
    for (T i : v)
        fout << i << " ";
    return fout;
}
ll rdn(int y, int m, int d) {
    /* Rata Die day one is 0001-01-01 */
    if (m < 3)
        y--, m += 12;
    return 365 * y + y / 4 - y / 100 + y / 400 + (153 * m - 457) / 5 + d - 306;
}
/* Direction arrays */
/*int dx[] = {1,-1,0,0}, dy[] = {0,0,1,-1};                             */ // 4Direction
/*int dx[] = {1,-1,0,0,1,1,-1,-1}, dy[] = {0,0,1,-1,1,-1,1,-1};         */ // 8Direction
/* int dx[] = {1,-1,1,-1,2,2,-2,-2} , dy[] = {2,2,-2,-2,1,-1,1,-1};     */ // KnightDirection
/* int dx[] = {2,-2,1,1,-1,-1} , dy[] = {0,0,1,-1,1,-1};                */ // HexagonalDirection
/* int day[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}; */
vector<string>vv;
int n;
int level[209];
int maxi;
void bfs(int x) {
    queue<int>q;
    q.push(x);
    level[x] = 1;
    while(q.empty() == false) {
        int t = q.front();
        q.pop();
        maxi=max(maxi,level[t]);
        for(int i = 0; i < n; i++) {
            if(vv[t][i] == '1' && level[i] == -1) {
                level[i] = level[t] + 1;
                q.push(i);
            }
        }
    }
}
int main() {
    scanf("%d", &n);
    string s;
    for(int i = 0; i < n; i++) {
        cin >> s;
        vv.EB(s);
    }
    int ans = 0;
    for(int i = 0; i < n; i++) {
        maxi = 0;
        memset(level, -1, sizeof level);
        bfs(i);
        for(int j = 0; j < n; j++) {
            for(int k = 0; k < n; k++) {
                if(vv[j][k] == '1' && level[j] == level[k]) {
                    cout << "-1\n";
                    return 0;
                }
            }
        }
        ans = max(ans, maxi);
    }
    cout << ans  << "\n";
}


Measured memory_bytes: 256