#include <bits/stdc++.h>
#define int long long
using namespace std;
const int N = 15;
string s;
vector<vector<vector<int>>> prefix(N, vector<vector<int>>());
vector<vector<vector<int>>> prefix_sum(N, vector<vector<int>>());
int calculate_prefix(int color, int boarded, int index) {
int ret = 0;
for(int i = 0; i < N; i++) {
if((1 << i) & boarded) ret += prefix[color][index][i];
}
return ret;
}
int calculate_prefix_sum(int color, int boarded, int index) {
int ret = 0;
for(int i = 0; i < N; i++) {
if((1 << i) & boarded) ret += prefix_sum[color][index][i];
}
return ret;
}
int calculate_sum(int boarded) {
int ret = 0;
for(int i = 0; i < N; i++) {
if((1 << i) & boarded) ret += prefix[i].back()[i];
}
return ret;
}
int opt_cost(int color, int boarded, int seats) {
int n = prefix[color].size() - 1;
int l = 0;
int r = n;
int total_boarded = calculate_sum(boarded);
while(l != r) {
int mid = l + r + 1;
mid /= 2;
int cost = (mid * (mid - 1) + (n - mid) * (n - mid - 1)) / 2;
int prev = mid - 1;
cost -= (prev * (prev - 1) + (n - prev) * (n - prev - 1)) / 2;
cost += 2 * (2 * calculate_prefix(color, boarded, mid) - total_boarded);
if(cost > 0)
r = mid - 1;
else
l = mid;
}
int retpt1 = (l * (l - 1) + (n - l) * (n - l - 1)) / 2;
int ret = 2 * (2 * calculate_prefix_sum(color, boarded, l) + total_boarded * (n - l) - calculate_prefix_sum(color, boarded, n));
ret += retpt1;
return ret;
}
int32_t main() {
cin >> s;
vector<int> csum(N, 0);
for(int i = 0; i < N; i++) {
prefix[i].push_back(vector<int>(N));
for(int j = 0; j < N; j++) {
prefix[i][0][j] = 0;
}
}
for(int i = 0; i < s.size(); i++) {
csum[s[i] - 65]++;
prefix[s[i] - 65].push_back(csum);
}
prefix_sum = prefix;
for(int i = 0; i < N; i++) {
for(int k = 0; k < N; k++) {
for(int j = 1; j < prefix_sum[i].size(); j++) {
prefix_sum[i][j][k] += prefix_sum[i][j-1][k];
}
}
}
vector<int> state(1 << N, 0x7fffffffffffffff);
vector<int> currentstates;
state[0] = 0;
currentstates.push_back(0);
while(!currentstates.empty()) {
vector<int> newcurrentstates;
for(int st : currentstates) {
for(int b = 0; b < N; b++) {
if((1 << b) & st) continue;
if((1 << b) > st) newcurrentstates.push_back(st | (1 << b));
int cost = opt_cost(b, st, s.size());
int newstate = (1 << b) | st;
state[newstate] = min(state[newstate], state[st] + cost);
}
}
currentstates = newcurrentstates;
}
cout << state.back() / 2;
if(state.back() & 1) cout << ".5";
return 0;
}
