#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define all(x) (x).begin(), (x).end()
#define MP make_pair
const int N = 100500;
long long exp_inv(ll n){
return (long long) n * (n - 1); // should be divided by 4
}
ll dp[1 << 15];
vector<ll> pref[16][16];
vector<ll> suff[16][16];
void solve(){
string str;
cin >> str;
int n = (int)str.size();
vector<vector<int>> pos;
map<char, int> id;
for (int i = 0; i < n; i++){
if (id.find(str[i]) == id.end()){
id[str[i]] = (int) id.size();
pos.emplace_back();
}
pos[id[str[i]]].push_back(i);
}
int G = (int) pos.size();
for (int x = 0; x < G; x++){
int sz_x = (int) pos[x].size();
for (int y = 0; y < G; y++){
if (x == y) continue;
int sz_y = (int) pos[y].size();
vector<ll> &p = pref[x][y], &s = suff[x][y];
p.resize(sz_x);
s.resize(sz_x);
int j = 0;
for (int i = 0; i < sz_x; i++){
while (j < sz_y && pos[y][j] <= pos[x][i]) j++;
p[i] = j;
}
j = sz_y - 1;
for (int i = sz_x - 1; i >= 0; i--){
while (j >= 0 && pos[y][j] >= pos[x][i]) j--;
s[i] = sz_y - j - 1;
}
for (int i = 1; i < sz_x; i++) p[i] += p[i - 1];
for (int i = sz_x - 2; i >= 0; i--) s[i] += s[i + 1];
}
}
function<long long(int, int, int)> cost = [&](int mask, int c, int wall){
int sz = (int) pos[c].size();
long long res = 0;
for (int d = 0; d < G; d++){
if (!(mask & (1 << d))) continue;
if (wall > 0) res += pref[c][d][wall - 1];
if (wall < sz) res += suff[c][d][wall];
}
res *= 4;
res += exp_inv(wall) + exp_inv(sz - wall);
return res;
};
fill(dp, dp + (1 << G), 5e18);
dp[0] = 0;
for (int mask = 0; mask < (1 << G); mask++){
if (dp[mask] >= 1e18) continue;
for (int c = 0; c < G; c++){
if (mask & (1 << c)) continue;
int sz = (int) pos[c].size();
long long mn = 5e18;
int l = 0, r = sz;
while (r - l >= 3){
int m1 = (2 * l + r) / 3, m2 = (l + 2 * r) / 3;
ll f1 = cost(mask, c, m1), f2 = cost(mask, c, m2);
mn = min({mn, f1, f2});
if (f1 < f2){
r = m2;
} else {
l = m1;
}
}
for (int i = l; i <= r; i++) mn = min(mn, cost(mask, c, i));
int new_mask = mask | (1 << c);
dp[new_mask] = min(dp[new_mask], dp[mask] + mn);
}
}
cout << dp[(1 << G) - 1] / 4;
if (dp[(1 << G) - 1] % 4 != 0) cout << ".5";
cout << endl;
}
int main() {
ios_base::sync_with_stdio(false);
#ifdef LOCAL
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#endif
solve();
return 0;
}
