#include <bits/stdc++.h>
#define file(s) freopen(s".in", "r", stdin); freopen(s".out", "w", stdout);
#define adiyer(); ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define debug cout << "bug"; return;
#define bitcount(n) __builtin_popcountll(n)
#define all(x) x.begin(), x.end()
#define len(s) (int) s.size()
#define md ((l + r) >> 1)
#define pb push_back
#define S second
#define F first
// #define int long long
using namespace std;
typedef long long ll;
typedef long double ld;
const int dx[8] = {1, 0, -1, 0, 1, 1, -1, -1};
const int dy[8] = {0, 1, 0, -1, -1, 1, -1, 1};
const int N = 2e5 + 11;
const int MAX = 1e6;
const int mod = 1e9 + 7;
const long long inf = 1e9 + 10;
const double eps = 1e-9;
ll n;
ll a[N], dp[(1 << 16)], pr[30][N], sf[30][N], cnt[30][30][N];
string s, t;
vector < ll > g[N];
ll f(ll x, ll pos, ll msk){
ll ans = pos * (pos - 1) / 2 + (len(g[x]) - pos) * (len(g[x]) - pos - 1) / 2;
for(ll y = 0; y < 15; y++)
if(x != y && (msk >> y & 1))
ans += cnt[x][y][pos] * 2;
return ans;
}
void output(){
cin >> s, n = len(s);
for(ll i = 0; i < n; i++) a[i] = s[i] - 'A', g[a[i]].pb(i);
for(ll x = 0; x < 15; x++){
for(ll y = 0; y < 15; y++){
if(x == y) continue;
for(ll i = 0; i < len(g[x]) + 5; i++) pr[x][i] = sf[x][i] = 0;
for(ll i = 0, j = 0; i < len(g[x]); i++){
while(j < len(g[y]) && g[y][j] <= g[x][i]) j++;
pr[x][i + 1] = pr[x][i] + j;
}
for(ll i = len(g[x]) - 1, j = len(g[y]) - 1; i >= 0; i--){
while(j >= 0 && g[y][j] >= g[x][i]) j--;
sf[x][i + 1] = sf[x][i + 2] + len(g[y]) - j - 1;
}
for(ll i = 0; i <= len(g[x]); i++) cnt[x][y][i] = pr[x][i] + sf[x][i + 1];
}
}
for(ll msk = 1; msk < (1 << 15); msk++){
dp[msk] = inf;
for(ll i = 0; i < 15; i++){
if((msk >> i & 1)){
ll l = 0, r = len(g[i]);
while(r - l > 5){
ll m1 = l + (r - l) / 3;
ll m2 = r - (r - l) / 3;
if(f(i, m1, msk) > f(i, m2, msk)) l = m1;
else r = m2;
}
for(ll j = l; j <= r; j++)
dp[msk] = min(dp[msk], dp[(msk ^ (1 << i))] + f(i, j, msk));
}
}
// cout << msk << ' ' << dp[msk] << '\n';
}
ll ans = dp[(1 << 15) - 1];
if(ans % 2) cout << ans / 2 << ".5";
else cout << ans / 2;
}
const bool cases = 0;
signed main(){
// file("disrupt");
adiyer();
int tt = 1;
if(cases) cin >> tt;
for(int i = 1; i <= tt; i++){
output();
}
}
