#include <bits/stdc++.h>
using namespace std;
int n, g;
string s;
long double get(long double x) {
return x * (x-1)/4;
}
int used[1111];
long double pref[100100];
long double suf[100100];
int was[1<<16][16];
long double dp[1<<16][16];
long double calc(int mask, int x) {
if(was[mask][x]) return dp[mask][x];
was[mask][x] = 1;
int A = 0;
int X = 0;
for(int i = 0; i < n; i++) {
pref[i+1] = pref[i];
if(s[i] == 'A' + x) {
pref[i+1] += A + X*0.5;
X++;
} else if(used[s[i] - 'A']) {
A++;
}
}
X = 0;
A = 0;
for(int i = n-1; i >= 0; i--) {
suf[i] = suf[i+1];
if(s[i] == 'A' + x) {
suf[i] += A + X * 0.5;
X++;
} else if(used[s[i] - 'A']){
A++;
}
}
long double ans = 1e18;
for(int i = 0; i < n; i++) {
ans = min(ans, pref[i] + suf[i]);
}
dp[mask][x] = ans;
return ans;
}
int main() {
cin >> s;
n = s.size();
for(int i = 0; i < n; i++) {
g = max(s[i] - 'A', g);
}
vector<int> p;
for(int i = 0; i <= g; i++) {
p.push_back(i);
}
//cout << g << "\n";
long double ans = 1e18;
do{
for(int i = 0; i <= g; i++) {
used[i] = 0;
}
long double cur = 0;
int mask = 0;
for(int x: p) {
cur += calc(mask, x);
mask |= (1<<x);
used[x] = 1;
}
ans = min(ans, cur);
}while(next_permutation(p.begin(), p.end()));
cout << fixed << setprecision(12) << ans << "\n";
}
