#include <bits/stdc++.h>
using namespace std;
#define int long long
#define all(v) v.begin(), v.end()
const int M = 100000, N = 15;
int pre[N][M],pre1[N][N][M],pre2[N][N][M],dp[1<<N],sz[N];
vector<int> a[N];
int get(int p,vector<int> v)
{
int ans=0;
for (int i:v)
ans+=pre[i][p];
return ans*2;
}
signed main()
{
ios::sync_with_stdio(0);
cin.tie(NULL), cout.tie(NULL);
cout<<fixed<<setprecision(10);
string s;
cin>>s;
int n=s.size();
for (int i=0;i<n;i++)
a[s[i]-'A'].push_back(i);
for (int i=0;i<N;i++)
{
sz[i]=a[i].size();
for (int j:a[i])
pre[i][j]++;
for (int j=1;j<M;j++)
pre[i][j]+=pre[i][j-1];
}
for (int i=0;i<N;i++)
for (int j=0;j<N;j++)
{
for (int k:a[i])
pre1[i][j][k]=(k?pre[j][k-1]:0),
pre2[i][j][k]=pre[j][M-1]-pre[j][k];
for (int k=1;k<M;k++)
pre1[i][j][k]+=pre1[i][j][k-1];
for (int k=M-2;k>=0;k--)
pre2[i][j][k]+=pre2[i][j][k+1];
}
int fin=0;
for (int m=1;m<(1<<N);m++)
{
if (__builtin_popcount(m)==1)
{
int p=31-__builtin_clz(m);
if (sz[p]) fin+=m;
else continue;
dp[m]=(sz[p]/2)*(sz[p]/2-1)/2+(sz[p]-sz[p]/2)*(sz[p]-sz[p]/2-1)/2;
continue;
}
dp[m]=n*(n-1)/2;
vector<int> v;
int su=0;
for (int p=0;p<N;p++)
if (m>>p&1 && sz[p]) v.push_back(p),su+=pre[p][M-1]*2;
for (int i:v)
{
su-=pre[i][M-1];
int s=-1,e=sz[i];
while (s+1<e)
{
int mid=(s+e)/2;
int p=get(a[i][mid],v)-pre[i][a[i][mid]];
if (p*2-1-su<=0)
s=mid;
else
e=mid;
}
int x=0;
for (int j:v)
{
int mu=1+(i!=j);
if (s>=0) x+=pre1[i][j][a[i][s]]*mu;
if (s+1<sz[i]) x+=pre2[i][j][a[i][s+1]]*mu;
}
dp[m]=min(dp[m],dp[m^(1<<i)]+x);
su+=pre[i][M-1];
}
}
// cout<<dp[3]<<endl;
if (dp[fin]%2) s=".5";
else s="";
cout<<dp[fin]/2<<s<<endl;
return 0;
}
