#include <bits/stdc++.h>
#define int ll
using namespace std;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define rng(i,c,n) for(int i=c;i<n;i++)
#define fi first
#define se second
#define pb push_back
#define sz(a) (int)a.size()
#define vec(...) vector<__VA_ARGS__>
#define _3CZAtRo ios::sync_with_stdio(0),cin.tie(0)
typedef long long ll;
using pii=pair<int,int>;
using vi=vector<int>;
void print(){cout<<'\n';}
template<class h,class...t>
void print(const h&v,const t&...u){cout<<v<<' ',print(u...);}
const int inf=1e10;
void chmin(int&a,const int&b){
a=min(a,b);
}
signed main(){
_3CZAtRo;
int n;
vi a;
{
string s;
cin>>s;
n=sz(s);
vi tmp;
rep(i,n){
tmp.pb(s[i]-'A');
}
sort(tmp.begin(),tmp.end());
tmp.erase(unique(tmp.begin(),tmp.end()),tmp.end());
rep(i,n){
int v=lower_bound(tmp.begin(),tmp.end(),s[i]-'A')-tmp.begin();
a.pb(v);
}
}
const int si=sz(set<int>(a.begin(),a.end()));
vec(vi) rbts(si);
rep(i,n){
rbts[a[i]].pb(i);
}
vec(vec(vi)) pf(si,vec(vi)(si,vi(n))),sf;
sf=pf;
rep(s,si){
rep(t,si){
if(s==t) continue;
int cnt=0;
rep(i,n){
if(i) pf[s][t][i]=pf[s][t][i-1];
if(a[i]==t){
pf[s][t][i]+=cnt;
}else if(a[i]==s){
cnt+=1;
}
}
cnt=0;
per(i,n){
if(i<n-1) sf[s][t][i]=sf[s][t][i+1];
if(a[i]==t){
sf[s][t][i]+=cnt;
}else if(a[i]==s){
cnt+=1;
}
}
}
}
auto af1=[&](int v,int msk,int id)->int{
int pos=(id==-1?id:rbts[v][id]);
int res=0;
rep(u,si){
if(msk>>u&1){
if(pos!=-1) res+=pf[u][v][pos];
if(pos+1<n) res+=sf[u][v][pos+1];
}
}
res=2*res;
if(id!=-1){
res+=((id+1)*id)/2+(sz(rbts[v])-id-1)*(sz(rbts[v])-id-2)/2;
}else{
res+=(sz(rbts[v])*(sz(rbts[v])-1))/2;
}
return res;
};
auto af0=[&](int v,int msk){
int sj=sz(rbts[v]);
int l=0,r=sj-1;
while(r-l>3){
int ml=(2*l+r)/3;
int mr=(l+2*r)/3;
int fl=af1(v,msk,ml);
int fr=af1(v,msk,mr);
if(fl<fr) r=mr;
else l=ml;
}
int res=af1(v,msk,-1);
rng(i,l,r+1){
res=min(res,af1(v,msk,i));
}
return res;
};
vi dp(1<<si,inf);
dp[0]=0;
rep(msk,1<<si){
int now=dp[msk];
rep(v,si){
if(!(msk>>v&1)){
int nmsk=msk|(1<<v);
int wit=af0(v,msk);
chmin(dp[nmsk],wit+now);
}
}
}
int ans=dp[(1<<si)-1];
cout<<ans/2<<(ans%2?".5":"")<<"\n";
}
