#include <bits/stdc++.h>
using std::vector;
using std::array;
using std::pair;
using std::tuple;
using ll = long long;
template <class F> struct fixed : private F {
explicit fixed(F&& f) : F(std::forward<F>(f)) {}
template <class... Args> decltype(auto) operator()(Args&&... args) const {
return F::operator()(*this, std::forward<Args>(args)...);
}
};
template <class T>
constexpr T infty = std::numeric_limits<T>::max() / 2;
template <class T>
void setmin(T& x, const T& y) {
if (x > y) {
x = y;
}
}
int main() {
std::ios_base::sync_with_stdio(false);
std::cin.tie(nullptr);
std::string S;
std::cin >> S;
const int N = (int)S.size();
const int G = 15;
array<vector<int>, G> pos = {};
for (int i = 0; i < N; ++i) {
pos[S[i] - 'A'].push_back(i);
}
array<vector<int>, G> accum = {};
accum.fill(vector(N + 1, 0));
for (int i = 0; i < N; ++i) {
for (int k = 0; k < G; ++k) {
accum[k][i + 1] = accum[k][i];
}
accum[S[i] - 'A'][i + 1] += 1;
}
array<array<vector<ll>, G>, G> precalc = {};
for (int i = 0; i < G; ++i) {
for (int j = 0; j < G; ++j) {
const int n = (int)pos[i].size();
precalc[i][j].resize(n + 1);
for (const int x : pos[i]) {
precalc[i][j][0] += accum[j][N] - accum[j][x];
}
for (int k = 0; k < n; ++k) {
const int x = pos[i][k];
ll next = precalc[i][j][k];
next -= accum[j][N] - accum[j][x];
next += accum[j][x];
precalc[i][j][k + 1] = next;
}
}
}
vector<ll> dp(1 << G, infty<ll>);
dp[0] = 0;
for (int set = 0; set < (1 << G); ++set) {
for (int add = 0; add < G; ++add) {
if (set >> add & 1) {
continue;
}
const int n = pos[add].size();
const auto calc = [&](const int k) {
ll ret = 0;
for (int i = 0; i < G; ++i) {
if (set >> i & 1) {
ret += precalc[add][i][k];
}
}
return ret * 2 + (ll)k * (k - 1) / 2 + (ll)(n - k) * (n - k - 1) / 2;
};
int l = -1, r = n + 1;
while (r - l > 2) {
const int m = (l + r) / 2;
if (calc(m) > calc(m + 1)) {
l = m;
} else {
r = m + 1;
}
}
setmin(dp[set | (1 << add)], dp[set] + calc(l + 1));
}
}
const ll ans = dp[(1 << G) - 1];
std::cout << ans / 2;
if (ans % 2 == 1) {
std::cout << ".5";
}
std::cout << '\n';
return 0;
}
