#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 int 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 = 1e5 + 11;
const int MAX = 1e6;
const int mod = 1e9 + 7;
const long long inf = 1e9 + 10;
const double eps = 1e-9;
ll n, m;
ll dp[(1 << 15)], p[N], ok[N];
string s, t;
void output(){
cin >> s, n = len(s);
for(ll i = 0; i < n; i++)
if(t.find(s[i]) == -1)
t.pb(s[i]), m++;
for(ll msk = 1; msk < (1 << m); msk++){
dp[msk] = inf;
for(ll i = 0; i < 15; i++) ok[i] = 0;
for(ll i = 0; i < m; i++)
if((msk >> i & 1))
ok[t[i] - 'A'] = 1;
for(ll i = 0; i < m; i++){
if((msk >> i & 1)){
ll val = 0, cur = 0;
for(ll pos = 0; pos < n; pos++){
p[pos] = 0;
if(s[pos] == t[i]) p[pos]++;
else if(ok[s[pos] - 'A']) p[pos] += 2;
if(pos) p[pos] += p[pos - 1];
}
for(ll pos = n - 1; pos >= 0; pos--){
if(s[pos] == t[i]) val += min(cur, (pos == 0 ? 0 : p[pos - 1]));
if(s[pos] == t[i]) cur++;
else if(ok[s[pos] - 'A']) cur += 2;
}
dp[msk] = min(dp[msk], dp[(msk ^ (1 << i))] + val);
}
}
// cout << msk << ' ' << dp[msk] << '\n';
}
if(dp[(1 << m) - 1] % 2 == 0) cout << dp[(1 << m) - 1] / 2;
else cout << dp[(1 << m) - 1] / 2 << ".5";
}
const bool cases = 0;
signed main(){
// file("disrupt");
adiyer();
int tt = 1;
if(cases) cin >> tt;
for(int i = 1; i <= tt; i++){
output();
}
}
