#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define all(x) x.begin(), x.end()
int main() {
string s;
cin >> s;
int n = s.size(), g = *max_element(all(s)) - 'A' + 1;
ll ev[g][1 << g]{};
auto c = [&] (int x) { return (ll) x * (x - 1) / 2; };
for (int j = g; j--;) {
vector<int> v;
for (int i = 0; i < n; ++i) {
if (s[i] - 'A' == j) v.emplace_back(i);
}
if (v.empty()) continue;
struct : vector<int> {
vector<ll> ps{0}, iw{0};
void init() {
for (int i = 0; i < size(); ++i) {
ps.emplace_back(ps.back() + (*this)[i]);
iw.emplace_back(iw.back() + (i + 1) * (*this)[i]);
}
}
ll operator()(int l, int r) {
return iw[r + 1] - iw[l] - l * (ps[r + 1] - ps[l]);
}
} l[g], r[g];
for (int k = g; k--;) {
l[k].resize(v.size() + 1);
r[k].resize(v.size() + 1);
}
for (int i = n, idx = -1; i--;) {
if (~idx) l[s[i] - 'A'][idx] += 1 + (s[i] - 'A' != j);
if (s[i] - 'A' == j) ++idx;
}
for (int i = 0, idx = -1; i < n; ++i) {
if (~idx) r[s[i] - 'A'][idx] += 1 + (s[i] - 'A' != j);
if (s[i] - 'A' == j) ++idx;
}
for (int k = g; k--;) {
l[k].init();
r[k].init();
}
auto gl = [&] (int i, int m) {
ll cur = 0;
m |= 1 << j;
for (int k = g; k--;) cur += ((m >> k) & 1) * l[k](v.size() - i, v.size() - 1);
return cur;
};
auto gr = [&] (int i, int m) {
ll cur = 0;
m |= 1 << j;
for (int k = g; k--;) cur += ((m >> k) & 1) * r[k](i, v.size() - 1);
return cur;
};
for (int m = 1 << g; m--;) {
if ((m >> j) & 1) continue;
ev[j][m] = min(gr(0, m), gl(v.size(), m));
if (v.size() == 1) continue;
int i = 1;
for (int k = 17; k--;) {
if (i + (1 << k) + 1 >= v.size()) continue;
i += 1 << k;
if (gl(i + 1, m) + gr(i + 1, m) >= gl(i, m) + gr(i, m)) i -= 1 << k;
}
ev[j][m] = min(ev[j][m], gl(i, m) + gr(i, m));
if (i + 1 < v.size()) ev[j][m] = min(ev[j][m], gl(i + 1, m) + gr(i + 1, m));
}
}
ll dp[1 << g];
memset(dp, 0x3f, sizeof dp);
dp[0] = 0;
for (int m = 0; m < (1 << g); ++m) {
for (int i = g; i--;) {
if ((m >> i) & 1) continue;
dp[m | (1 << i)] = min(dp[m | (1 << i)], dp[m] + ev[i][m]);
}
}
cout << dp[(1 << g) - 1] / 2;
if (dp[(1 << g) - 1] & 1) cout << ".5";
}
