#pragma GCC target("sse,sse2,sse3,ssse3,sse4,sse4.1,sse4.2,abm,mmx,avx,avx2,popcnt,tune=native")
#pragma GCC optimize("fast-math")
//#pragma GCC optimize("Ofast")
/*#pragma GCC optimize("section-anchors")
#pragma GCC optimize("profile-values,profile-reorder-functions,tracer")
#pragma GCC optimize("vpt")
#pragma GCC optimize("rename-registers")
#pragma GCC optimize("move-loop-invariants")
#pragma GCC optimize("unswitch-loops")
#pragma GCC optimize("function-sections")
#pragma GCC optimize("data-sections")
#pragma GCC optimize("branch-target-load-optimize")
#pragma GCC optimize("branch-target-load-optimize2")
#pragma GCC optimize("btr-bb-exclusive")*/
//#pragma GCC optimize("inline")
//#pragma comment(linker, "/STACK:16777216")
#define _CRT_SECURE_NO_WARNINGS
#include <chrono>
#include <set>
#include <map>
#include <deque>
#include <string>
#include <cstdint>
#include <cmath>
#include <queue>
#include <cassert>
#include <random>
#include <bitset>
#include <iomanip>
#include <numeric>
#include <time.h>//////////////
#include <ctime>
#include <climits>
#include <string>
#include <cstdio>
#include <vector>
#include <cstdlib>
#include <iostream>
#include <algorithm>
#include <unordered_map>
#include <unordered_set>
//++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++
//#define endl '\n'
#define mp make_pair
#define pbc push_back
#define pob pop_back()
#define empb emplace_back
#define queuel queue<long long>
#define sqr(a) ((a) * (a))
#define lsqr(a) (ld(a) * a)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define pin(p) cin >> p.first >> p.second;
#define uniq(a) sort(all(a));(a).resize(unique(all(a)) - a.begin());
#define rev(v) reverse(v.begin(), v.end());
#define sout(s, c) for (auto i : s) cout << i << c;
#define pout(p) cout << p.first << " " << p.second;
#define er(v, l, r) erase(v.begin() + l, v.begin() + r);
#define vin(v) for (ll i = 0; i < v.size(); ++i) cin >> v[i];
#define vout(v, c) for (int i = 0; i < v.size(); ++i) cout << v[i] << c;
#define pushi(v, a) for (int i = 0; i < a.size(); ++i) v.push_back(a[i]);
#define fastio() ios_base::sync_with_stdio(0); cout.tie(0); cin.tie(0); srand(time(NULL))
#define dab(v) for(auto i:v)cout<<i<<' ';
#define sp system("pause")
#define left left228
#define calc calc228
#define next next228
#define type type1337
#define right right228
//++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++
using namespace std;
//++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
//++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++
const ld EPS = 1e-14	;
const ld EPS2 = 1e-12;
const ld PI = acos(-1);
int mod = (int)998244353;
const int MOD7 = 1000000007;
const int MOD9 = 1000000009;
const int a228 = 18;
const ll INF = 1e18;
const int inf = 1e9;
mt19937 rnd(time(0));
const ll kekmod = 1791791791;
const ll bestmod = 1148822869;
const int MAXN = 101;
vector<int> rg[MAXN];
vector<int> used(MAXN);
int cnt = 0;
void dfs(int v)
{
	cnt++;
	used[v] = 1;
	for (int i : rg[v])
		if (!used[i]) dfs(i);
}
signed main()
{
	fastio();
	int n;
	cin >> n;
	for (int i = 0; i < n; ++i)
	{
		string s;
		cin >> s;
		for (int j = 0; j < n; ++j)
		{
			if (s[j] == '1')
			{
				rg[j].pbc(i);
			}
		}
	}
	ld ans = 0;
	for (int i = 0; i < n; ++i)
	{
		used.assign(MAXN, 0);
		cnt = 0;
		dfs(i);
		ans += (ld)1 / cnt;
	}
	cout << fixed << setprecision(20) << ans;
	sp;
}
#include<bits/stdc++.h>
using namespace std;

int n,a[105][105],b[105][105];

int main()
{
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		string s;
		cin>>s;
		b[i][i]=1;
		for(int j=1;j<=n;j++)
			if(s[j-1]=='1')	
				a[i][j]=b[j][i]=1;
	}
	for(int t=1;t<=n;t++)
		for(int i=1;i<=n;i++)
			for(int j=1;j<=n;j++)
				b[i][j]=b[i][j]|(b[i][t]&b[t][j]);
	double ans=0;
	for(int i=1;i<=n;i++)
	{
		int cnt=0;
		for(int j=1;j<=n;j++)
			if(b[i][j])	cnt++;
		ans+=1.0/cnt;
	}
	printf("%.10lf",ans);
}







