#include<bits/stdc++.h>
using ll=long long;
#define rep(i,a,b) for(ll i=(ll)a;i<(ll)b;++i)
#define rrep(i,a,b) for(ll i=(ll)b-1;i>=(ll)a;--i)
using namespace std;
int main(){
string S;cin>>S;
vector<int>s;
for(auto&e:S)s.push_back(e-'A');
const int n=s.size();
const int g=*max_element(s.begin(),s.end())+1;
vector idx(g,vector<int>());
rep(i,0,n)idx[s[i]].push_back(i);
vector prefix(g,vector<ll>(n,0));
auto suffix=prefix;
vector suml(g,vector<ll>(n,0));
auto sumr=suml;
rep(i,0,n){
prefix[s[i]][i]++;
suffix[s[i]][i]++;
}
rep(i,0,g){
rep(j,0,n-1)prefix[i][j+1]+=prefix[i][j];
rrep(j,0,n-1)suffix[i][j]+=suffix[i][j+1];
}
vector<int>last(g,-1);
rep(i,0,n){
rep(j,0,g)suml[j][i]=prefix[j][i];
if(last[s[i]]!=-1)rep(j,0,g)suml[j][i]+=suml[j][last[s[i]]];
last[s[i]]=i;
}
last=vector<int>(g,-1);
rrep(i,0,n){
rep(j,0,g)sumr[j][i]=suffix[j][i];
if(last[s[i]]!=-1)rep(j,0,g)sumr[j][i]+=sumr[j][last[s[i]]];
last[s[i]]=i;
}
auto calc1=[&](ll bit,ll i)->int {
int ok=-1,ng=idx[i].size();
while(ng-ok>1){
int mid=(ok+ng)>>1;
int p=idx[i][mid];
ll l=0,r=0;
rep(j,0,g){
if((bit>>j)&1)l+=prefix[j][p]*2,r+=suffix[j][p]*2;
else if(i==j)l+=prefix[j][p],r+=suffix[j][p];
}
if(l<=r)ok=mid;
else ng=mid;
}
return ok;
};
auto calc2=[&](ll bit,ll i,int m)->ll {
ll ret=0;
if(m!=-1){
int p=idx[i][m];
rep(j,0,g){
if((bit>>j)&1)ret+=suml[j][p]*2;
}
}
if(m!=(int)idx[i].size()-1){
int p=idx[i][m+1];
rep(j,0,g){
if((bit>>j)&1)ret+=sumr[j][p]*2;
}
}
ret+=(ll)m*(m+1)/2;
ret+=(ll)(idx[i].size()-m-1)*(idx[i].size()-m-2)/2;
return ret;
};
vector dp(1<<g,LLONG_MAX>>2);
dp[0]=0;
rep(bit,0,1<<g){
rep(i,0,g){
if((bit>>i)&1)continue;
if(idx[i].empty())dp[bit^(1<<i)]=min(dp[bit^(1<<i)],dp[bit]);
else{
int m=calc1(bit,i);
ll cost=calc2(bit,i,m);
//cerr<<bit<<" "<<i<<" "<<m<<" "<<cost<<endl;
dp[bit^(1<<i)]=min(dp[bit^(1<<i)],dp[bit]+cost);
}
}
}
//for(auto&i:dp)cerr<<i<<endl;
cout<<dp.back()/2.0<<endl;
}
