#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];
long long costPref[MAX_G][MAX_G][MAX_N + 2], costSuf[MAX_G][MAX_G][MAX_N + 2];
unordered_map<char, int> lit;
double expectedInversions( int n ) {
return (double)n * (n - 1) / 4;
}
double queryCost( int c, int mask, int i ) {
double cost = expectedInversions( frecv[c][i] ) + expectedInversions( frecv[c][n] - frecv[c][i] );
for ( int d = 0; d < g; d++ ) {
if ( (mask >> d) & 1 )
cost += costPref[c][d][i] + costSuf[c][d][i + 1];
}
return cost;
}
double solve( int c, int mask ) {
int l = 0, r = n;
while ( r - l > 2 ) {
int mid1 = (l * 2 + r) / 3;
int mid2 = (l + r * 2) / 3;
if ( queryCost( c, mask, mid1 ) > queryCost( c, mask, mid2 ) )
l = mid1;
else if ( queryCost( c, mask, mid1 ) < queryCost( c, mask, mid2 ) )
r = mid2;
else {
l++;
r--;
}
}
double bst = (double)n * n;
for ( int i = max( 0, l - 10 ); i <= min( n, r + 10 ); i++ )
bst = min( bst, queryCost( c, mask, i ) );
return bst;
}
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);
}
for ( int c = 0; c < g; c++ ) {
for ( int d = 0; d < g; d++ ) {
if ( c == d )
continue;
int cnt;
cnt = 0;
for ( int i = 1; i <= n; i++ ) {
costPref[c][d][i] = costPref[c][d][i - 1];
if ( s[i] == c )
costPref[c][d][i] += cnt;
if ( s[i] == d )
cnt++;
}
cnt = 0;
for ( int i = n; i >= 1; i-- ) {
costSuf[c][d][i] = costSuf[c][d][i + 1];
if ( s[i] == c )
costSuf[c][d][i] += cnt;
if ( s[i] == d )
cnt++;
}
}
}
cout << fixed << setprecision( 1 );
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;
}
