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

#define REP(i,n) for(ll i=0;i<(ll)n;i++)
#define dump(x)  cerr << "Line " << __LINE__ << ": " <<  #x << " = " << (x) << "\n";
#define spa << " " <<
#define fi first
#define se second
#define ALL(a)  (a).begin(),(a).end()
#define ALLR(a)  (a).rbegin(),(a).rend()

using ld = long double;
using ll = long long;
using ull = unsigned long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pdd = pair<ld, ld>;

template<typename T> using V = vector<T>;
template<typename T> using P = pair<T, T>;
template<typename T> vector<T> make_vec(size_t n, T a) { return vector<T>(n, a); }
template<typename... Ts> auto make_vec(size_t n, Ts... ts) { return vector<decltype(make_vec(ts...))>(n, make_vec(ts...)); }
template<class S, class T> ostream& operator << (ostream& os, const pair<S, T> v){os << "(" << v.first << ", " << v.second << ")"; return os;}
template<typename T> ostream& operator<<(ostream &os, const vector<T> &v) { for (auto &e : v) os << e << ' '; return os; }
template<class T> ostream& operator<<(ostream& os, const vector<vector<T>> &v){ for(auto &e : v){os << e << "\n";} return os;}
struct fast_ios { fast_ios(){ cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;

template <class T> void UNIQUE(vector<T> &x) {sort(ALL(x));x.erase(unique(ALL(x)), x.end());}
template<class T> bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T> bool chmin(T &a, const T &b) { if (a>b) { a=b; return 1; } return 0; }
void fail() { cout << -1 << '\n'; exit(0); }
inline int popcount(const int x) { return __builtin_popcount(x); }
inline int popcount(const ll x) { return __builtin_popcountll(x); }
template<typename T> void debug(vector<vector<T>>&v,ll h,ll w){for(ll i=0;i<h;i++)
{cerr<<v[i][0];for(ll j=1;j<w;j++)cerr spa v[i][j];cerr<<"\n";}};
template<typename T> void debug(vector<T>&v,ll n){if(n!=0)cerr<<v[0];
for(ll i=1;i<n;i++)cerr spa v[i];
cerr<<"\n";};

const ll INF = (1ll<<62);
// const ld EPS   = 1e-10;
// const ld PI    = acos(-1.0);
const ll mod = (int)1e9 + 7;
//const ll mod = 998244353;

ll graph_bfs(V<V<ll>> &G, ll s){
    // sは始点のリスト
    const int N = G.size();
    vector<int> dist(N, -1);
    queue<int> qu;

    // initialization
    qu.push(s);
    dist[s] = 0;

    while(!qu.empty()){
        int now = qu.front();qu.pop();
        for(auto next: G[now]){
            if(dist[next] != -1) continue;
            dist[next] = dist[now] + 1;
            qu.push(next);
        }
    }

    ll res = 0;
    REP(i, N) if(dist[i] >= 0) res++;
    return res;
}

int main(){

    ll N;
    cin >> N;
    V<string> S(N);
    REP(i, N) cin >> S[i];

    V<V<ll>> G(N);
    REP(i, N){
        REP(j, N){
            if(S[i][j] == '1'){
                G[j].push_back(i);
            }
        }
    }

    ld res = 0;

    REP(i, N){
        res += (ld)1.0/(graph_bfs(G, i));
    }

    cout << res << endl;


    return 0;
}
#pragma GCC optimize("O2,unroll-loops")
#pragma GCC target("avx,avx2,sse,sse2,ssse3,sse4.1,sse4.2,popcnt")
#include<bits/extc++.h>
#define all(x) begin(x), end(x)
using namespace std;
using ll = long long;
const int maxn = 1<<11, mod = 1e9 + 7;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
vector<int> g[maxn];
int vis[maxn];
int dfs(int v) {
	vis[v] =1;
	int res = 1;
	for(auto i : g[v]) if(!vis[i]) res += dfs(i);
	return res;
}
signed main() {
	cin.tie(0)->sync_with_stdio(0);
	int n;
	char c;
	cin >> n;
	for(int i = 1; i <= n; i++)
		for(int j = 1; j <= n; j++) {
			cin >> c;
			if(c == '1') g[j].push_back(i);
		}
	long double ans = 0;
	for(int i = 1; i <= n; i++) {
		fill(all(vis), 0);
		ans += 1./dfs(i);
	}
	cout << fixed << setprecision(15) << ans << endl;
}
