#include <bits/stdc++.h>   #pragma comment(linker,  /STACK:1000000000 )   using namespace std;   inline void solve();   int main() {     ios::sync_with_stdio(0);     cin.tie(0);     cout.tie(0);     solve();   }   string abc =  abcdefghijklmnopqrstuvwxyz ;   string ABC =  ABCDEFGHIJKLMNOPQRSTUVWXYZ ;   string digits =  0123456789 ;   void solve() {     vector<long long> ind[30];     string s;     cin >> s;     long long n = s.length();     for (long long i = 0; i < n; i++) ind[s[i] -  a ].push_back(i);     double ans = 0;     s = s + s;     long long p[30] = {0};     for (long long i = 0; i < 26; i++) {       for (long long len = 1; len < n; len++) {         long long c[30] = {0};         for (long long l = 0; l < ind[i].size(); l++) {           c[s[ind[i][l] + len] -  a ]++;         }         long long cnt = 0;         for (long long j = 0; j < 30; j++)           if (c[j] == 1) cnt++;         p[i] = max(p[i], cnt);       }       ans += p[i] * 1. / n;     }     cout << setprecision(15) << fixed << ans;   }   