#include <bits/stdc++.h>
using namespace std;
long long counter1;
long long n;
vector<long long> val;
vector<vector<long long> > l, r;
vector<vector<vector<long long> > > l2, r2;
vector<vector<long long> > groups;
long long dpSolve2(long long already_boarded, long long next, long long split){
long long ans = 0;
for (long long t = 0; t < counter1; ++t) {
long long tmp = l2[next][t][split] + r2[next][t][split];
if (already_boarded & (1ll << t)) {
ans += 2 * tmp;
} else if (t == next) {
ans += tmp;
}
}
return ans;
}
long long dpSolve(long long already_boarded, long long next){
long long low = 0, high = groups[next].size() + 1;
while (high - low > 1) {
long long mid1 = (high + low) / 2 - 1;
long long mid2 = mid1 + 1;
long long c1 = dpSolve2(already_boarded, next, mid1);
long long c2 = dpSolve2(already_boarded, next, mid2);
if (c1 < c2){
high = mid2;
}
else{
low = mid1 + 1;
}
}
long long ans = dpSolve2(already_boarded, next, low);
return ans;
}
long long calc_costs(){
vector<long long> dp(1ll << counter1, 1e18);
dp[0] = 0;
for (long long i = 1; i < 1ll << counter1; ++i) {
for (long long t = 0; t < counter1; ++t) {
if (!(i & (1ll << t))) continue;
long long parent = i & ~(1ll << t);
dp[i] = min(dp[i], dp[parent] + dpSolve(parent, t));
}
}
return dp[(1ll << counter1) - 1];
}
int main(){
string s;
cin >> s;
n = s.size();
map<char, char> types;
for (char& c: s) {
if (!types.count(c)) {
char id = static_cast<char>(types.size());
types[c] = id;
}
c = types[c];
}
counter1 = types.size();
val.assign(counter1, 0);
for (char c: s){
val[c]++;
}
groups.resize(counter1);
for (long long i = 0; i < n; ++i) {
groups[s[i]].push_back(i);
}
l = r = vector<vector<long long> >(counter1, vector<long long>(n));
vector<long long> tmp_cnt(counter1, 0);
for (size_t i = 0; i < n; ++i) {
for (size_t j = 0; j < counter1; ++j) {
l[j][i] = tmp_cnt[j];
r[j][i] = val[j] - tmp_cnt[j];
}
++tmp_cnt[s[i]];
--r[s[i]][i];
}
vector<vector<long long> > dpLeft, dpRight;
dpLeft = dpRight = vector<vector<long long> >(counter1, vector<long long>(counter1, 0));
l2 = r2 = vector<vector<vector<long long> > >(counter1, vector<vector<long long> >(counter1, {0}));
for (long long i = 0; i < n; i++) {
for (long long j = 0; j < counter1; ++j) {
dpLeft[s[i]][j] += l[j][i];
dpRight[s[n - i - 1]][j] += r[j][n - i - 1];
}
for (long long k = 0; k < counter1; ++k) {
l2[s[i]][k].push_back(dpLeft[s[i]][k]);
r2[s[n - i - 1]][k].push_back(dpRight[s[n - i - 1]][k]);
}
}
for (long long i = 0; i < counter1; ++i) {
for (long long j = 0; j < counter1; ++j) {
reverse(r2[i][j].begin(), r2[i][j].end());
}
}
long long ans = calc_costs();
cout << ans / 2 << ((ans % 2) ? ".5" : "") << "\n";
}
