#include <bits/stdc++.h>
using namespace std;
const int MAX_G = 15;
const int MAX_N = 1e5;
int n, g;
string s;
double dp[1 << MAX_G];
int frecv[MAX_G][MAX_N + 1];
double costPref[MAX_N + 2], costSuf[MAX_N + 2];
unordered_map<char, int> lit;
double expectedInversions( int n ) {
return (double)n * (n - 1) / 4;
}
double solve( int c, int mask ) {
int crt, prv;
crt = prv = 0;
costPref[0] = 0;
for ( int i = 1; i <= n; i++ ) {
costPref[i] = costPref[i - 1];
if ( s[i] == c ) {
crt++;
costPref[i] += prv;
}
if ( (mask >> s[i]) & 1 )
prv++;
}
crt = prv = 0;
costSuf[n + 1] = 0;
for ( int i = n; i >= 1; i-- ) {
costSuf[i] = costSuf[i + 1];
if ( s[i] == c ) {
crt++;
costSuf[i] += prv;
}
if ( (mask >> s[i]) & 1 )
prv++;
}
double best = (double)n * n;
for ( int i = 0; i <= n; i++ ) {
double cost = costPref[i] + expectedInversions( frecv[c][i] ) + costSuf[i + 1] + expectedInversions( frecv[c][n] - frecv[c][i] );
best = min( best, cost );
}
return best;
}
int main() {
cin >> s;
n = s.size();
s = " " + s;
g = 0;
for ( int i = 1; i <= n; i++ ) {
if ( lit[s[i]] == 0 )
lit[s[i]] = ++g;
s[i] = lit[s[i]] - 1;
}
for ( int c = 0; c < g; c++ ) {
for ( int i = 1; i <= n; i++ )
frecv[c][i] = frecv[c][i - 1] + (s[i] == c);
}
cout << fixed << setprecision( 5 );
for ( int mask = 1; mask < (1 << g); mask++ ) {
dp[mask] = (double)n * n;
for ( int c = 0; c < g; c++ ) {
if ( (mask >> c) & 1 )
dp[mask] = min( dp[mask], dp[mask - (1 << c)] + solve( c, mask - (1 << c) ) );
}
}
cout << dp[(1 << g) - 1];
return 0;
}
