#include "bits/stdc++.h"
#define int long long
#define double long double
#define all(v) v.begin() , v.end()
#define sz(a) (int) a.size()
using namespace std;
const int LOG = 15;
const double INF = 1e18;
const int N = 1e5 + 5;
int suf[LOG][LOG][N];
int pre[LOG][LOG][N];
int ar[N],n,G;
vector<double> dp((1LL<<LOG) + 5,INF);
vector<int> pos[LOG];
void calc(){
for(int i=0;i<G;i++){
for(int j=0;j<G;j++){
if(i==j) continue;
int res=0,kac=0;
for(int x=1;x<=n;x++){
if(ar[x]==j) kac++;
else if(ar[x]==i) res+=kac;
pre[i][j][x]=res;
}
}
}
for(int i=0;i<G;i++){
for(int j=0;j<G;j++){
if(i==j) continue;
int res=0,kac=0;
for(int x=n;x>=1;x--){
if(ar[x]==j) kac++;
else if(ar[x]==i) res+=kac;
suf[i][j][x]=res;
}
}
}
}
double Get_Cost(int ind,int u,int mask){
int le = ind + 1, ri = sz(pos[u]) - ind - 1;
double res = le*(le-1)/4.0L + ri*(ri-1)/4.0L;
//cout << "ilk: " << res << '\n';
for(int i=0;i<G;i++){
if(ind==-1) break;
if(!(mask>>i&1)) continue;
res += pre[u][i][pos[u][ind]];
}
//cout << "sec: " << res << '\n';
for(int i=0;i<G;i++){
if(ind+1>=sz(pos[u])) break;
if(!(mask>>i&1)) continue;
res += suf[u][i][pos[u][ind+1]];
}
//cout << "tri: " << res << '\n';
return res;
}
void _(){
string s;
cin >> s;
n=sz(s);
vector<int> zip;
for(int i=0;i<n;i++) zip.push_back(s[i]-'A');
sort(all(zip));
zip.erase(unique(all(zip)),zip.end());
for(int i=1;i<=n;i++) ar[i]=lower_bound(all(zip),s[i-1]-'A')-zip.begin();
dp[0] = 0;
G = sz(zip);
for(int i=1;i<=n;i++) pos[ar[i]].push_back(i);
calc();
//cout << Get_Cost(0,ar[2],(1<<ar[1])) << '\n';
for(int mask=1;mask<(1LL<<G);mask++){
for(int u=0;u<G;u++){
if(!(mask>>u&1)) continue;
int l = -1, r = sz(pos[u]) - 1;
while(r-l>4){
int mid = (l + r) / 2;
if( Get_Cost(mid,u,mask^(1<<u)) > Get_Cost(mid+1,u,mask^(1<<u)) )
l=mid;
else
r=mid;
}
// cout << mask << ' ' << u << ' ' << l+1 << '\n';
for(int ll=l;ll<=r;ll++)
dp[mask] = min(dp[mask], dp[mask^(1<<u)] + Get_Cost(ll,u,mask^(1<<u)) );
}
}
cout << dp[(1LL<<G)-1] << '\n';
}
int32_t main(){
cin.tie(0); ios::sync_with_stdio(0);
cout << fixed << setprecision(16);
int tc=1;//cin >> tc;
while(tc--) _();
return 0;
}
