#pragma GCC optimize("Ofast","unroll-loops")
#include <bits/stdc++.h>
using namespace std;
#define int long long
int32_t main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
const int G = 15;
vector<vector<int>> groups(G);
string s;
cin >> s;
int N = s.size();
vector<vector<int>> peopleBeforeInGroup(N+1,vector<int>(G));
for(int i=0;i<N;i++){
groups[s[i]-'A'].emplace_back(i+1);
peopleBeforeInGroup[i+1]=peopleBeforeInGroup[i];
peopleBeforeInGroup[i+1][s[i]-'A']++;
}
vector prefixAns(G,vector (G,vector (N+1,0ll)));
vector suffixAns(G,vector (G,vector (N+1,0ll)));
for(int top=0;top<G;top++){
for(int bottom=0;bottom<G;bottom++){
for(int idx=0;idx<groups[top].size();idx++){
int i = groups[top][idx];
if(idx)prefixAns[top][bottom][idx]=prefixAns[top][bottom][idx-1];
prefixAns[top][bottom][idx]+=2ll*peopleBeforeInGroup[i-1][bottom];
}
for(int idx=groups[top].size()-1;idx>=0;idx--){
int i = groups[top][idx];
if(idx!=N)suffixAns[top][bottom][idx]=suffixAns[top][bottom][idx+1];
suffixAns[top][bottom][idx]+=2ll*(groups[bottom].size()-peopleBeforeInGroup[i][bottom]);
}
}
for(int&i:prefixAns[top][top])i/=2;
for(int&i:suffixAns[top][top])i/=2;
}
vector<int> DP((1<<G),1e12);
DP[0]=0;
for(int mask=1;mask<(1<<G);mask++){
int tot = 0;
for(int x=0;x<G;x++)if(mask&(1<<x)){
tot+=groups[x].size();
}
for(int top=0;top<G;top++)if(mask&(1<<top)){
int ans = 0;
int breakPoint = lower_bound(groups[top].begin(),groups[top].end(),0,[&](const int x,const int b){
int currMine = peopleBeforeInGroup[x][top]-1;
int currOther = 0;
for(int i=0;i<G;i++)if((mask&(1<<i)) and i!=top)currOther+=peopleBeforeInGroup[x][i];
return currMine+2ll*currOther<=groups[top].size()-1ll-currMine+2ll*(tot-groups[top].size()-currOther);
}) - groups[top].begin();
for(int i=0;i<G;i++)if(mask&(1<<i)){
if(breakPoint)ans+=prefixAns[top][i][breakPoint-1];
if(breakPoint<groups[top].size())ans+=suffixAns[top][i][breakPoint];
}
DP[mask]=min(DP[mask],DP[mask^(1<<top)]+ans);
}
}
cout << DP[(1<<G)-1]/2;
if(DP[(1<<G)-1]&1)cout<<".5";
cout << '\n';
}
