#include <bits/stdc++.h>
using namespace std;
#define int long long
#define INF (int)1e18
#define f first
#define s second
mt19937_64 RNG(chrono::steady_clock::now().time_since_epoch().count());
int n, k;
const int K = 16;
const int N = 1e5 + 69;
int dp[1 << K]; //store 2 * value
int F[N][K]; //fenwick for all positions
vector <int> pos[K];
int add[K][K][N]; //value to add if i was already there, j is newly added, and we add it by prefix of size k, and rest suffix
void upd(int x, int j){
for (int i = x; i <= n; i += i & (-i)) F[i][j]++;
}
int query(int x, int j){
int res = 0;
for (int i = x; i; i -= i & (-i)) res += F[i][j];
return res;
}
void pre(){
for (int i = 0; i < k; i++){
for (int j = 0; j < k; j++){
if (i == j) continue;
int sz = pos[j].size();
int curr = 0;
for (int pref = 1; pref <= sz; pref++){
curr += query(pos[j][pref - 1], i);
add[i][j][pref] = curr;
}
curr = 0;
for (int pref = sz - 1; pref >= 0; pref--){
curr += query(n, i) - query(pos[j][pref], i);
add[i][j][pref] += curr;
}
}
}
}
int f(int pref, int mask, int i){
int ans = 0;
int tot = pos[i].size();
ans += pref * (pref - 1) / 2;
ans += (tot - pref) * (tot - pref - 1) / 2;
// if (i == 0){
// cout << pref << " " << ans << "\n";
// }
for (int j = 0; j < k; j++){
if (mask >> j & 1){
ans += 2 * add[j][i][pref];
}
}
return ans;
}
int transition(int mask, int i){
int l = 0, r = pos[i].size();
while (r - l > 2){
int m1 = (2 * l + r) / 3;
int m2 = (l + 2 * r) / 3;
int x1 = f(m1, mask, i);
int x2 = f(m2, mask, i);
if (x1 > x2) l = m1;
else r = m2;
}
int ans = INF;
for (int j = l; j <= r; j++) ans = min(ans, f(j, mask, i));
// cout << mask << " " << i << " " << ans << " " << dp[mask] << "\n";
return dp[mask] + ans;
}
void Solve()
{
string s; cin >> s;
n = s.length();
k = 15;
for (int i = 0; i < n; i++){
pos[s[i] - 'A'].push_back(i + 1);
upd(i + 1, s[i] - 'A');
}
pre();
for (int i = 1; i < (1 << k); i++) dp[i] = INF;
for (int i = 1; i < (1 << k); i++){
for (int j = 0; j < k; j++){
if (i >> j & 1){
dp[i] = min(dp[i], transition(i ^ (1 << j), j));
}
}
}
int ans = dp[(1 << k) - 1];
if (ans & 1) cout << (ans/2) << ".5\n";
else cout << (ans/2) << "\n";
}
int32_t main()
{
auto begin = std::chrono::high_resolution_clock::now();
ios_base::sync_with_stdio(0);
cin.tie(0);
int t = 1;
// cin >> t;
for(int i = 1; i <= t; i++)
{
//cout << "Case #" << i << ": ";
Solve();
}
auto end = std::chrono::high_resolution_clock::now();
auto elapsed = std::chrono::duration_cast<std::chrono::nanoseconds>(end - begin);
cerr << "Time measured: " << elapsed.count() * 1e-9 << " seconds.\n";
return 0;
}
