#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("Ofast")
#define ll long long
const int mxn=1e5+5,mxg=15;
int g,n,a[mxn],cnt=0,all[mxg+5];
string s;
ll dp[(1<<mxg)],res[(1<<mxg)][mxg+5],z=1,zz=2;
ll pre[mxn][mxg+5][mxg+5],suf[mxn][mxg+5][mxg+5],num[mxn];
vector<int>v[mxg+5];
ll cal(ll mask,int c,int y){
ll sum=0,x=v[c][y];
for(int i=1;i<=cnt;i++){
if(mask&(1<<(i-1))){
sum+=pre[x+1][c][i]+suf[x+1][c][i];
}
}
sum*=2;
sum+=y*(y-1)/2;
y=all[c]-y;
sum+=y*(y-1)/2;
return sum;
}
ll f(ll mask,ll c){
ll res=cal(mask,c,0);
int L=1,R=v[c].size()-1;
while(L<R){
int mid=(L+R)/2;
ll x=cal(mask,c,mid);
ll y=cal(mask,c,mid+1);
if(x<=y)
R=mid;
else
L=mid+1;
}
res=min(res,cal(mask,c,L));
//cout<<mask<<" "<<c<<" "<<res<<'\n';
return res;
}
int main(){
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
cin>>s;
n=s.size();
for(int i=1;i<=mxg;i++)
v[i].push_back(-1);
for(int i=0;i<n;i++){
int x=s[i];
a[x]=(a[x]==0)?++cnt:a[x];
x=a[x];
all[x]+=z;
v[x].push_back(i);
}
for(int i=0;i<n;i++){
int x=s[i];
x=a[x];
for(int j=1;j<=cnt;j++){
for(int k=1;k<=cnt;k++){
if(j==k)continue;
pre[i+1][j][k]=pre[i][j][k];
if(x==j)
pre[i+1][j][k]+=num[k];
}
}
num[x]++;
}
memset(num,0,sizeof num);
for(int i=n-1;i>=0;i--){
int x=s[i];
x=a[x];
for(int j=1;j<=cnt;j++){
for(int k=1;k<=cnt;k++){
if(j==k)continue;
suf[i][j][k]=suf[i+1][j][k];
if(x==j)
suf[i][j][k]+=num[k];
}
}
num[x]++;
}
for(int i=1;i<(1<<cnt);i++){
dp[i]=1e18;
for(int j=0;j<cnt;j++){
if(i&(1<<j)){
int y=i-(1<<j);
dp[i]=min(dp[i],dp[y]+f(y,j+1));
}
}
}
cout<<dp[(1<<cnt)-1]/2;
if(dp[(1<<cnt)-1]%2)
cout<<".5";
return 0;
}
