#include <bits/stdc++.h>
using namespace std ;
const int MAX = 1e5 + 10 ;
int arr[MAX] , mark[MAX] ;
int n ;
long double pref[MAX] , suff[MAX] ;
string s ;
long double calc(int x)
{
long double sum = 0 ;
for(int i = 0 ; i < x ; ++i)
sum += 0.5 * i ;
return sum ;
}
vector<int>occ[30] ;
int main()
{
ios_base::sync_with_stdio(0) ;
cin.tie(0) ;
cin>>s ;
n = s.size() ;
for(int i = 0 ; i < n ; ++i)
occ[s[i]-'A'].push_back(i) ;
vector<char>v ;
for(int i = 'A' ; i < 'A'+7 ; ++i)
v.push_back(i) ;
long double ans = 1e18 ;
do
{
for(int i = 0 ; i < n ; ++i)
mark[i] = pref[i] = suff[i] = 0 ;
long double ex = 0 ;
for(auto &c : v)
{
if(!occ[c-'A'].size())
continue ;
long double cnt = 0 , cnt2 = 0 ;
int last = -1 ;
for(int i = 0 ; i < n ; ++i)
{
cnt += mark[i] ;
if(s[i] != c)
continue ;
pref[i] = cnt + 0.5 * cnt2 ;
if(last != -1)
pref[i] += pref[last] ;
++cnt2 , last = i ;
}
cnt = 0 , cnt2 = 0 , last = -1 ;
for(int i = n-1 ; i >= 0 ; --i)
{
cnt += mark[i] ;
if(s[i] != c)
continue ;
suff[i] = cnt + 0.5 * cnt2 ;
if(last != -1)
suff[i] += suff[last] ;
++cnt2 , last = i ;
mark[i] = 1 ;
}
int sz = occ[c-'A'].size() ;
long double Min = min(pref[occ[c-'A'][sz-1]] , suff[occ[c-'A'][0]]) ;
for(int i = 0 ; i < sz-1 ; ++i)
Min = min(Min , pref[occ[c-'A'][i]] + suff[occ[c-'A'][i+1]]) ;
ex += Min ;
}
ans = min(ans , ex) ;
}while(next_permutation(v.begin() , v.end())) ;
return cout<<fixed<<setprecision(12)<<ans<<"\n" , 0 ;
}
