#include <bits/stdc++.h>
#define rep(a,b,c) for(ll a = b; a < c; a++)
#define rep2(a,b,c) for(ll a = c - 1; a >=b; a--)
#define all(x) (x).begin(), (x).end()
#define pb push_back
#define x first
#define y second
using namespace std;
using ll = long long;
using tl = tuple<ll, ll, ll>;
using pl = pair<ll, ll>;
using pi = pair<int, int>;
using ld = long double;

const int MAX = 2e5 + 3;
string S;
map<char, int> m;
ll ans;

int main() {
	cin.tie(0); cout.tie(0); ios_base::sync_with_stdio(false);
	cin >> S;
	rep2(i, 2, S.size()) {
		m[S[i]]++;
		if (S[i - 2] == S[i - 1] && S[i - 1] != S[i]) {
			ans += S.size() - i - m[S[i - 2]];
			m.clear();
			m[S[i - 2]] = S.size() - i;
		}
	}
	cout << ans;
	return 0;
}
#include <bits/stdc++.h>
#define MP make_pair
#define PB push_back
#define int long long
#define st first
#define nd second
#define rd third
#define FOR(i, a, b) for(int i =(a); i <=(b); ++i)
#define RE(i, n) FOR(i, 1, n)
#define FORD(i, a, b) for(int i = (a); i >= (b); --i)
#define REP(i, n) for(int i = 0;i <(n); ++i)
#define VAR(v, i) __typeof(i) v=(i)
#define FORE(i, c) for(VAR(i, (c).begin()); i != (c).end(); ++i)
#define ALL(x) (x).begin(), (x).end()
#define SZ(x) ((int)(x).size())
#define __builtin_ctz __builtin_ctzll
#define __builtin_clz __builtin_clzll
#define __builtin_popcount __builtin_popcountll
using namespace std;
template<typename TH> void _dbg(const char* sdbg, TH h) { cerr<<sdbg<<"="<<h<<"\n"; }
template<typename TH, typename... TA> void _dbg(const char* sdbg, TH h, TA... t) {
  while(*sdbg != ',') { cerr<<*sdbg++; } cerr<<"="<<h<<","; _dbg(sdbg+1, t...);
}
#ifdef LOCAL
#define debug(...) _dbg(#__VA_ARGS__, __VA_ARGS__)
#define debugv(x) {{cerr <<#x <<" = "; FORE(itt, (x)) cerr <<*itt <<", "; cerr <<"\n"; }}
#else
#define debug(...) (__VA_ARGS__)
#define debugv(x)
#define cerr if(0)cout
#endif
#define next ____next
#define prev ____prev
#define left ____left
#define hash ____hash
typedef long long ll;
typedef long double LD;
typedef pair<int, int> PII;
typedef pair<ll, ll> PLL;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<ll> VLL;
typedef vector<pair<int, int> > VPII;
typedef vector<pair<ll, ll> > VPLL;

template<class C> void mini(C&a4, C b4){a4=min(a4, b4); }
template<class C> void maxi(C&a4, C b4){a4=max(a4, b4); }
template<class T1, class T2>
ostream& operator<< (ostream &out, pair<T1, T2> pair) { return out << "(" << pair.first << ", " << pair.second << ")";}
template<class A, class B, class C> struct Triple { A first; B second; C third;
  bool operator<(const Triple& t) const { if (st != t.st) return st < t.st; if (nd != t.nd) return nd < t.nd; return rd < t.rd; } };
template<class T> void ResizeVec(T&, vector<int>) {}
template<class T> void ResizeVec(vector<T>& vec, vector<int> sz) {
  vec.resize(sz[0]); sz.erase(sz.begin()); if (sz.empty()) { return; }
  for (T& v : vec) { ResizeVec(v, sz); }
}
typedef Triple<int, int, int> TIII;
template<class A, class B, class C>
ostream& operator<< (ostream &out, Triple<A, B, C> t) { return out << "(" << t.st << ", " << t.nd << ", " << t.rd << ")"; }
template<class T> ostream& operator<<(ostream& out, vector<T> vec) { out<<"("; for (auto& v: vec) out<<v<<", "; return out<<")"; }
template<class T> ostream& operator<<(ostream& out, set<T> vec) { out<<"("; for (auto& v: vec) out<<v<<", "; return out<<")"; }
template<class L, class R> ostream& operator<<(ostream& out, map<L, R> vec) { out<<"("; for (auto& v: vec) out<<v<<", "; return out<<")"; }


const int N = 111;
typedef bitset<N> B;

int32_t main() {

  ios_base::sync_with_stdio(0);
  cout << fixed << setprecision(10);
  cerr << fixed << setprecision(10);
  cin.tie(0);
  //double beg_clock = 1.0 * clock() / CLOCKS_PER_SEC;
  
  int n;
  cin>>n;
  vector<B> dis(n + 2);
  RE (i, n) {
    string s;
    cin>>s;
    dis[i][i] = 1;
    RE (j, n) {
      if (s[j - 1] == '1') {
        dis[j][i] = 1;
      }
    }
  }
  LD res = 0;
  RE (i, n) {
    VI vis(n + 2);
    int cnt = 0;
    function<void(int)> Dfs = [&](int v) {
      vis[v] = 1;
      cnt++;
      RE (j, n) {
        if (dis[v][j] == 1 && !vis[j]) {
          Dfs(j);
        }
      }
    };
    Dfs(i);
    res += 1. / cnt;
  }
//   RE (k, n) {
//     RE (i, n) {
//       RE (j, n) {
//         dis[i] |= dis[i][k] & dis[k][j];
//       }
//     }
//   }
//   LD res = 0;
//   RE (i, n) {
//     res += 1. / dis[i].count();
//   }
  cout<<res<<endl;
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  return 0;
}
