//consider scc graph
//u -> v
//if u bad then v must be bad
//so every ingoing edge into v must be good and sum of sub(tree?graph?) must be >= minimal parent
//i dont even need scc,only scc is if all values are equal okay yes
#include <bits/stdc++.h>
using namespace std;
#define sz(a) (int)(a.size())
#define all(a) a.begin(),a.end()
#define pb push_back
#define owo ios_base::sync_with_stdio(0);cin.tie(0);
typedef long long int ll;
typedef long double ld;
const int MAXN = 1e5+5;
int g[MAXN];
ll dp[MAXN],pref[MAXN],suff[MAXN];
ll cost[15][15][MAXN];
vector<int>p[15];
int main()
{
string s;
cin>>s;
int n = sz(s);
int m = 0;
for(int i=0;i<n;i++){
g[i] = s[i] - 'A';
m = max(g[i],m);
p[g[i]].pb(i);
}
m++;
for(int i=0;i<m;i++){
for(int j=0;j<m;j++){
if(i==j)continue; //j go after i
int s0 = sz(p[i]);
int s1 = sz(p[j]);
//last "l" at here
int ptr = -1;
ll a = 0,b = 0;
for(int k=0;k<s1;k++){
while(ptr+1<s0 && p[i][ptr+1] < p[j][k]){
ptr++;
a+=2;
}
b+=a;
cost[i][j][k+1] = b;
}
a = b = 0;
ptr = s0;
for(int k=s1-1;k>=0;k--){
while(ptr-1>=0 && p[i][ptr-1] > p[j][k]){
ptr--;
a+=2;
}
b+=a;
cost[i][j][k]+= b;
}
}
}
for(int mask=0;mask<(1<<m);mask++)dp[mask] = 1e18;
dp[0] = 0;
for(int mask=0;mask<(1<<m);mask++){
vector<int>v;
for(int j=0;j<m;j++){
if(mask&(1<<j))v.pb(j);
}
for(int j=0;j<m;j++){
if(mask&(1<<j))continue;
int s1 = sz(p[j]);
for(int k=0;k<=s1;k++){
ll c = 0;
for(int x:v)c+=cost[x][j][k];
c+=k * 1LL *(k-1)/2;
c+=(s1-k) * 1LL *(s1-k-1)/2;
dp[mask+(1<<j)] = min(dp[mask+(1<<j)],dp[mask]+c);
}
}
}
ld ans = dp[(1<<m)-1];
ans/=2;
cout<<fixed<<setprecision(5)<<ans<<'\n';
}
