#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define fi first
#define se second
#define for1(i,j,k) for(int i=j;i<=k;i++)
#define for2(i,j,k) for(int i=j;i>=k;i--)
#define for3(i,j,k,l) for(int i=j;i<=k;i+=l)
#define bit(n,i) ((n>>i)&1)
#define all(x) x.begin(),x.end()
#pragma GCC optimize("O2,unroll-loops")
#pragma GCC target("avx,avx2,bmi,bmi2,sse,sse2,sse3,ssse3,sse4,popcnt")
#define int long long
typedef long long ll;
typedef pair<int,int> pii;
typedef double ld;
typedef pair<ld,ld> pdd;
typedef pair<ll,ll> pll;
const ll maxn=1e5+5;
const ll offset=1e18;
const ll block_sz=317;
const ll inf=1e18;
const ll mod=1e9+7;
int n,a[maxn],cost[(1<<15)+2][16],dp[(1<<15)+2],id[16],g=-1,pre[16][maxn],suf[16][maxn];
vector<int> L[16],prep[16][16],suff[16][16];
string s;
void dbg(int mask)
{
bitset<5> xxx(mask);
cout << xxx;
}
int f(int x,int k,int mask)
{
int tt=L[k].size();
int sum=((x-1)*x/2) + ((tt-x)*(tt-x-1)/2);
if (x==tt)
{
for1(i,0,g-1)
{
if ((mask>>i)&1)
{
sum+=2*prep[k][i][tt-1];
}
}
return sum;
}
//cerr<<k<<' '<<x<<' '<< "wtf\n";
for1(i,0,g-1)
{
if ((mask>>i)&1)
{
sum+=2*suff[k][i][x];
//cerr<<k<<' '<<i<<' '<<x<<suff[k][i][x]<<'\n';
}
}
if (x==0)return sum;
for1(i,0,g-1)
{
if ((mask>>i)&1)
{
sum+=2*prep[k][i][x-1];
//cerr<<k<<' '<<i<<' '<<x<< prep[k][i][x-1]<<'\n';
}
}
return sum;
}
void sol()
{
cin >> s;
n=s.size();
s=' '+s;
for1(i,0,15) id[i]=-1;
for1(i,1,n)
{
if (id[s[i]-'A']==-1)
{
id[s[i]-'A']=++g;
}
L[id[s[i]-'A']].pb(i);
a[i]=id[s[i]-'A'];
//cerr<< a[i]<<'\n';
}
g++;
for1(i,1,n)
{
for1(j,0,g-1)
{
pre[j][i]=pre[j][i-1]+((a[i]==j)?1:0);
}
}
for2(i,n,1)
{
for1(j,0,g-1)
{
suf[j][i]=suf[j][i+1]+((a[i]==j)?1:0);
}
}
for1(i,0,g-1)
{
for1(j,0,g-1)
{
//if (i==j) continue;
prep[i][j].resize(L[i].size()+1);
prep[i][j][0]=pre[j][L[i][0]];
for1(k,1,L[i].size()-1)
{
prep[i][j][k]=prep[i][j][k-1]+pre[j][L[i][k]];
}
suff[i][j].resize(L[i].size()+1);
suff[i][j][L[i].size()-1]=suf[j][L[i][L[i].size()-1]];
for2(k,L[i].size()-2,0)
{
suff[i][j][k]=suff[i][j][k+1]+suf[j][L[i][k]];
}
}
}
for1(i,0,g-1)
{
int k1=L[i].size()/2;
int k2=L[i].size()-k1;
cost[0][i]=(k1*(k1-1)+k2*(k2-1))/2;
}
for1(mask,1,(1<<g)-1)
{
for1(i,0,g-1)
{
int dem=0,tt=L[i].size();
if (!((mask>>i)&1))
{
int l=0,r=tt,mid;
while (r-l>1)
{
mid=l+r>>1;
if (f(mid,i,mask)<f(mid+1,i,mask))
{
r=mid;
}
else
{
l=mid;
}
}
cost[mask][i]=min(f(l,i,mask),f(l+1,i,mask));
//if (mask==3 && i==2 ) cerr<< "adsad "<< l+1<<' '<<f(l+1,i,mask)<<' '<<f(l,i,mask) <<'\n';
}
}
}
// cerr<< f(2,0,2)<<'\n';
//// bitset<4> xxx(2);
//// cout << xxx<<'\n';
// cout << cost[3][2]<<'\n';
for1(mask,0,(1<<g)-1) dp[mask]=inf;
dp[0]=0;
for1(mask,0,(1<<g)-1)
{
for1(i,0,g-1)
{
if (!((mask>>i)&1))
{
dp[mask^(1<<i)]=min(dp[mask^(1<<i)],dp[mask]+cost[mask][i]);
}
}
// dbg(mask);
// cout<<' '<<dp[mask]<<'\n';
}
//cerr<< g<<'\n';
cout << dp[(1<<g)-1]/2;
if (dp[(1<<g)-1]&1) cout << ".5";
}
int32_t main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
// freopen("GROUPDIV.inp","r",stdin);
// freopen("GROUPDIV.out","w",stdout);
int t=1;//cin >> t;
while (t--)
{
sol();
}
}
/*
3 1
12345678
?11
*/
