// Bolatulu
#include <bits/stdc++.h>
// #include <art.h>
/*
#pragma GCC target ("avx2")
#pragma GCC optimization ("O3")
#pragma GCC optimization ("unroll-loops")
*/
typedef long long ll;
typedef unsigned long long ull;
typedef double db;
#define pb push_back
#define eb emplace_back
#define ins insert
#define F first
#define S second
#define md (tl+tr)/2
#define TL v+v,tl,md
#define TR v+v+1,md+1,tr
#define Tl t[v].l,tl,md
#define Tr t[v].r,md+1,tr
#define all(x) (x).begin(),(x).end()
#define yes cout << "YES\n"
#define no cout << "NO\n"
#define int long long
// #define file(s) freopen(s".in", "r", stdin); freopen(s".out", "w", stdout);
using namespace std;
int binpow(int a,int n,int M) {
if (n==0)
return 1;
if (n%2!=0)
return (a * binpow(a,n-1,M))%M;
int z=binpow(a,n/2,M);
return (z*z)%M;
}
const ll INF = 1e18+7;
const int N = 5e5+7;
int n,dp[N],a[N],c[N],p[N];
string s;
vector <int> v[N],d[N];
void solve() {
cin >> s;
n=s.size();
s=" "+s;
int g=0;
for (int i=1;i<=n;i++) {
g=max(g,(int)(s[i]-'A'+1));
d[s[i]-'A'].pb(i);
}
for (int i=0;i<g;i++)
p[(1<<i)]=i;
for (int mask=1;mask<(1<<g);mask++) {
for (int i=0;i<g;i++)
c[i]=0;
vector <int> vm;
int j=0,mn=p[mask];
for (auto now : v[mask]) {
while (j<d[mn].size() and d[mn][j]<now) {
vm.pb(d[mn][j]);
j++;
}
vm.pb(now);
}
while (j<d[mn].size()) {
vm.pb(d[mn][j]);
j++;
}
int x=0;
for (auto i : vm) {
int bit=s[i]-'A';
if (mask>>bit&1) {
a[i]=x*2-c[bit];
x++;
c[bit]++;
}
}
for (int i=0;i<g;i++)
c[i]=0;
x=0;
reverse(all(vm));
for (auto i : vm) {
int bit=s[i]-'A';
if (mask>>bit&1) {
a[i]=min(a[i],x*2-c[bit]);
x++;
c[bit]++;
}
}
for (int i=0;i<g;i++)
c[i]=0;
reverse(all(vm));
for (auto i : vm) {
int bit=s[i]-'A';
if (mask>>bit&1)
c[bit]+=a[i];
}
dp[mask]=INF;
for (int i=0;i<g;i++) {
if (mask>>i&1)
dp[mask]=min(dp[mask^(1<<i)]+c[i],dp[mask]);
else if (v[mask^(1<<i)].empty()){
v[mask^(1<<i)]=vm;
p[mask^(1<<i)]=i;
}
}
v[mask].clear();
}
int ans=dp[(1<<g)-1];
if (ans%2!=0)
cout << ans/2 << ".5";
else
cout << ans/2;
}
signed main() {
// file("jenga");
ios_base::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);
int test = 1;
// cin >> test;
while (test--) {
solve();
if (test)
cout << '\n';
}
return 0;
}
