#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
constexpr ll INF = LLONG_MAX / 10;
int type_cnt;
int n;
vector<ll> cnt;
vector<vector<ll>> l, r;
vector<vector<vector<ll>>> l2, r2;
vector<vector<int>> groups;
ll get_cost(int already_boarded, int next, int split)
{
ll result = 0;
for(int t = 0; t < type_cnt; t ++)
{
ll tmp = l2[next][t][split] + r2[next][t][split];
if (already_boarded & (1ll << t))
result += 2 * tmp;
else if (t == next)
result += tmp;
}
return result;
}
ll get_cost(int already_boarded, int next)
{
int mini = 0, maxi = groups[next].size() + 1;
while (maxi - mini > 1)
{
int m1 = (maxi + mini) / 2 - 1;
int m2 = m1 + 1;
ll c1 = get_cost(already_boarded, next, m1);
ll c2 = get_cost(already_boarded, next, m2);
if (c1 < c2)
maxi = m2;
else mini = m1 + 1;
}
ll result = get_cost(already_boarded, next, mini);
return result;
}
ll calc_costs()
{
vector<ll> dp(1ll << type_cnt, INF);
dp[0] = 0;
for(int i = 1; i < 1ll << type_cnt; i ++)
{
for(int t = 0; t < type_cnt; t ++)
{
if (!(i & (1ll << t)))
continue;
int parent = i & ~(1ll << t);
dp[i] = min(dp[i], dp[parent] + get_cost(parent, t));
}
}
return dp[(1ll << type_cnt) - 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];
}
type_cnt = types.size();
cnt.assign(type_cnt, 0);
for(char c: s)
cnt[c] ++;
groups.resize(type_cnt);
for(int i = 0; i < n; i ++)
groups[s[i]].push_back(i);
l = r = vector<vector<ll>>(type_cnt, vector<ll>(n));
vector<ll> tmp_cnt(type_cnt, 0);
for (int i = 0; i < n; i ++)
{
for (int j = 0; j < type_cnt; j ++)
{
l[j][i] = tmp_cnt[j];
r[j][i] = cnt[j] - tmp_cnt[j];
}
tmp_cnt[s[i]] ++;
r[s[i]][i] --;
}
vector<vector<ll>> tmp_costs_l, tmp_costs_r;
tmp_costs_l = tmp_costs_r = vector<vector<ll>>(type_cnt, vector<ll>(type_cnt, 0));
l2 = r2 = vector<vector<vector<ll>>>(type_cnt, vector<vector<ll>>(type_cnt, {0}));
for (int i = 0; i < n; i ++)
{
for (int j = 0; j < type_cnt; j ++)
{
tmp_costs_l[s[i]][j] += l[j][i];
tmp_costs_r[s[n - i - 1]][j] += r[j][n - i - 1];
}
for (int k = 0; k < type_cnt; ++k)
{
l2[s[i]][k].push_back(tmp_costs_l[s[i]][k]);
r2[s[n - i - 1]][k].push_back(tmp_costs_r[s[n - i - 1]][k]);
}
}
for(int i = 0; i < type_cnt; i ++)
for(int j = 0; j < type_cnt; j ++)
reverse(r2[i][j].begin(), r2[i][j].end());
auto result = calc_costs();
cout << result / 2 << ((result % 2) ? ".5" : "") << "\n";
}
