#include <bits/stdc++.h>
using namespace std;
#define int ll
#define endl '\n' //comment for interactive
#define fast_io ios::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define pb push_back
#define re resize
#define ff first
#define ss second
#define all(x) (x).begin(), (x).end()
#define all1(x) (x).begin()+1, (x).end()
#define loop(i, n) for(int i = 0; i < n; i++)
#define loop1(i, n) for(int i = 1; i <= n; i++)
#define print(x) cout << #x << ": " << x << endl << flush
typedef long long ll;
typedef vector<int> vi;
typedef vector<double> vd;
typedef array<int, 2> ii;
typedef array<int, 3> ti;
typedef vector<ii> vii;
typedef vector<ti> vti;
typedef vector<vi> vvi;
typedef priority_queue<int> pq;
template<class T> bool ckmin(T&a, T b) { bool B = a > b; a = min(a, b); return B; }
template<class T> bool ckmax(T&a, T b) { bool B = a < b; a = max(a, b); return B; }
const int inf = 1e17;
double cst(int x) {
return (double) x * (x-1) / 4;
}
void solve() {
string s;
cin >> s;
int n = s.size();
vvi pos(26);
loop(i, n)
pos[s[i]-'A'].pb(i);
vi ch;
loop(i, 26) if(!pos[i].empty())
ch.pb(i);
int g = ch.size();
vi id(26);
loop(i, g) id[ch[i]] = i;
if(g == 1) {
cout << setprecision(16) << cst(n/2) + cst((n+1)/2) << endl;
return;
}
vd dp(1 << g, inf);
dp[0] = 0;
loop(pre, 1 << g) {
bitset<15> prev(pre);
loop(ch, g) if(!prev[ch]) {
int nxt = pre + (1 << ch);
double cost = inf;
vd left(n);
vd right(n+1);
int cnt = 0, oth = 0;
for(int i = 0; i < n; i++) {
if(i) left[i] = left[i-1];
if(prev[id[s[i]-'A']]) oth++;
else if(id[s[i]-'A'] == ch) {
cnt++;
left[i] += oth;
left[i] += cst(cnt);
left[i] -= cst(cnt-1);
}
}
cnt = 0, oth = 0;
for(int i = n-1; i >= 0; i--) {
right[i] = right[i+1];
if(prev[id[s[i]-'A']]) oth++;
else if(id[s[i]-'A'] == ch) {
cnt++;
right[i] += oth;
right[i] += cst(cnt);
right[i] -= cst(cnt-1);
}
}
loop(i, n)
ckmin(cost, left[i] + right[i+1]);
ckmin(dp[nxt], dp[pre] + cost);
}
}
cout << setprecision(16) << dp[(1 << g) - 1] << endl;
}
signed main() {
fast_io;
int t = 1; //cin >> t;
while(t--)
solve();
return 0;
}
