#include <bits/stdc++.h>
using namespace std;
#define int long long
#define ii pair<int,int>
#define fi first
#define se second
#define endl '\n'
#define puf push_front
#define pof pop_front
#define pub push_back
#define pob pop_back
#define lb lower_bound
#define ub upper_bound
#define rep(x,s,e) for (int x=(s)-((s)>(e));x!=(e)-((s)>(e));((s)<(e))?x++:x--)
#define all(x) (x).begin(),(x).end()
#define sz(x) (int) (x).size()
mt19937 rng(chrono::system_clock::now().time_since_epoch().count());
const int BUF=100005;
struct node{
int arr[200010]={};
int query(int i,int j){
i+=BUF,j+=BUF+1;
int res=0;
while (i<j){
if (i&1) res+=arr[i++];
if (j&1) res+=arr[--j];
i>>=1,j>>=1;
}
return res;
}
};
int n;
string s;
vector<int> pos[15];
node root[15][15][2];
int cnt[15];
int get0(int u,int mask,int l,int r){
int res=0;
rep(v,0,15) if (mask&(1<<v)) res+=root[u][v][0].query(l,r);
return res;
}
int get1(int u,int mask,int l,int r){
int res=0;
rep(v,0,15) if (mask&(1<<v)) res+=root[u][v][1].query(l,r);
return res;
}
int memo[1<<15];
signed main(){
cin.tie(0);
cout.tie(0);
cin.sync_with_stdio(false);
cin>>s;
n=sz(s);
rep(x,0,n) pos[s[x]-'A'].pub(x);
rep(x,0,n){
rep(y,0,15) root[s[x]-'A'][y][0].arr[x+BUF]=cnt[y]*(s[x]-'A'==y?1:2);
cnt[s[x]-'A']++;
}
memset(cnt,0,sizeof(cnt));
rep(x,n,0){
rep(y,0,15) root[s[x]-'A'][y][1].arr[x+BUF]=cnt[y]*(s[x]-'A'==y?1:2);
cnt[s[x]-'A']++;
}
rep(x,0,15) rep(y,0,15) rep(z,0,2) rep(i,BUF,0){
root[x][y][z].arr[i]=root[x][y][z].arr[i<<1]+root[x][y][z].arr[i<<1|1];
}
memset(memo,63,sizeof(memo));
memo[0]=0;
rep(mask,0,1<<15) rep(bit,0,15) if ((mask&(1<<bit))==0){
int nm=mask|(1<<bit);
int lo=-1,hi=sz(pos[bit]),mi;
while (hi-lo>1){
mi=hi+lo>>1;
if (get0(bit,nm,pos[bit][mi],pos[bit][mi]) < get1(bit,nm,pos[bit][mi],pos[bit][mi])){
lo=mi;
}
else{
hi=mi;
}
}
int res=memo[mask];
if (0<=lo) res+=get0(bit,nm,0,pos[bit][lo]);
if (hi<sz(pos[bit])) res+=get1(bit,nm,pos[bit][hi],100004);
memo[nm]=min(memo[nm],res);
}
int ans=memo[(1<<15)-1];
cout<<ans/2; if (ans%2) cout<<".5"; cout<<endl;
}
