/**
____ ____ ____ ____ ____
||a |||t |||o |||d |||o ||
||__|||__|||__|||__|||__||
|/__\|/__\|/__\|/__\|/__\|
**/
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N_MAX = 100000;
const int G_MAX = 15;
int G, N;
int group[N_MAX];
vector <int> inGroup[G_MAX];
mt19937 rnd(0);
void input () {
string S;
cin >> S;
// for (int i = 0; i < 100000; i++) {
// S += (char) (rnd() % 15 + 'A');
// }
N = (int) S.size();
bool occ[26];
fill(occ, occ + 26, false);
for (int i = 0; i < N; i++) {
group[i] = (int) (S[i] - 'A');
occ[group[i]] = true;
}
int id[26];
for (int g = 0; g < 26; g++) {
if (occ[g] == true) {
id[g] = G++;
}
}
for (int i = 0; i < N; i++) {
group[i] = id[group[i]];
inGroup[group[i]].push_back(i);
}
}
int L[N_MAX], R[N_MAX];
int pref[N_MAX][G_MAX], suff[N_MAX][G_MAX];
ll prefSum[N_MAX][G_MAX], suffSum[N_MAX][G_MAX];
void precalc () {
for (int i = 0; i < N; i++) {
if (i > 0) {
for (int g = 0; g < G; g++) {
pref[i][g] = pref[i - 1][g];
}
}
pref[i][group[i]]++;
}
for (int i = N - 1; i >= 0; i--) {
if (i < N - 1) {
for (int g = 0; g < G; g++) {
suff[i][g] = suff[i + 1][g];
}
}
suff[i][group[i]]++;
}
int last[G_MAX];
fill(last, last + G, -1);
for (int i = 0; i < N; i++) {
L[i] = last[group[i]];
last[group[i]] = i;
if (L[i] != -1) {
for (int g = 0; g < G; g++) {
prefSum[i][g] = prefSum[L[i]][g];
}
}
for (int g = 0; g < G; g++) {
prefSum[i][g] += pref[i][g];
}
}
fill(last, last + G, -1);
for (int i = N - 1; i >= 0; i--) {
R[i] = last[group[i]];
last[group[i]] = i;
if (R[i] != -1) {
for (int g = 0; g < G; g++) {
suffSum[i][g] += suffSum[R[i]][g];
}
}
for (int g = 0; g < G; g++) {
suffSum[i][g] += suff[i][g];
}
}
}
ll f (int mask, int g, int k) {
ll ret;
if (k == 0) {
int i = inGroup[g][0];
int gr = suff[i][g];
ret = (ll) gr * (gr - 1) / 2;
while (mask > 0) {
int h = __builtin_ctz(mask & -mask);
mask ^= (1 << h);
ret += 2 * suffSum[i][h];
}
} else {
int i = inGroup[g][k - 1];
int gl = pref[i][g], gr = suff[R[i]][g];
ret = (ll) gl * (gl - 1) / 2 + (ll) gr * (gr - 1) / 2;
while (mask > 0) {
int h = __builtin_ctz(mask & -mask);
mask ^= (1 << h);
ret += 2 * prefSum[i][h] + 2 * suffSum[R[i]][h];
}
}
return ret;
}
ll minEV[1 << G_MAX];
void update (ll &x, const ll &y) {
if (y < x) {
x = y;
}
}
int main () {
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
cout << fixed << setprecision(4);
input();
precalc();
fill(minEV, minEV + (1 << G), LLONG_MAX);
minEV[0] = 0;
for (int mask = 0; mask < (1 << G) - 1; mask++) {
for (int g = 0; g < G; g++) {
if (((mask >> g) & 1) == 0) {
int l = 0, r = (int) inGroup[g].size();
while (l < r) {
int a = (l * 2 + r + 2) / 3, b = (l + r * 2) / 3;
if (f(mask, g, a) < f(mask, g, b)) {
r = b;
} else {
l = a;
}
}
for (int k = max(0, l - 100); k <= min((int) inGroup[g].size(), l + 100); k++) {
update(minEV[mask ^ (1 << g)], minEV[mask] + f(mask, g, k));
}
}
}
}
ll answer = minEV[(1 << G) - 1];
if (answer % 2 == 0) {
cout << answer / 2 << "\n";
} else {
cout << answer / 2 << ".5\n";
}
return 0;
}
