#include <bits/stdc++.h>
#define IO_OP ios::sync_with_stdio(0), cin.tie(0)
#define F first
#define S second
#define V vector
#define PB push_back
#define EB emplace_back
#define MP make_pair
#define SZ(v) int((v).size())
#define ALL(v) (v).begin(), (v).end()
using namespace std;
typedef long long ll;
typedef pair<int, int> pi;
typedef V<int> vi;
const int INF = 1e9 + 7;
const ll oo = 1e18;
vi G[15];
ll dp[1 << 15];
void cmin(ll& a, ll b) {
a = min(a, b);
}
ll C2(int n) { return 1LL * n * (n - 1) / 2; }
signed main()
{
IO_OP;
string s; cin >> s;
int n = SZ(s);
for(int i = 0; i < n; i++)
G[s[i] - 'A'].PB(i);
vi groups;
for(int i = 0; i < 15; i++)
if(G[i].size())
groups.PB(i);
int g = SZ(groups);
V<V<V<ll>>> aux(g, V<V<ll>>(g));
for(int i = 0; i < g; i++) {
for(int j = 0; j < g; j++) if(i != j) {
vi& gi = G[groups[i]], gj = G[groups[j]];
aux[i][j].resize(SZ(gj) + 1);
vi lef(SZ(gj)), rig(SZ(gj));
for(int k = 0, l = 0; k < SZ(gj); k++) {
while(l < SZ(gi) && gi[l] < gj[k])
l++;
lef[k] = l;
}
for(int k = SZ(gj) - 1, l = SZ(gi) - 1; k >= 0; k--) {
while(l >= 0 && gi[l] > gj[k])
l--;
rig[k] = SZ(gi) - 1 - l;
}
for(int k = 1; k < SZ(lef); k++)
lef[k] += lef[k - 1];
for(int k = SZ(rig) - 2; k >= 0; k--)
rig[k] += rig[k + 1];
for(int k = 0; k < SZ(aux[i][j]); k++) {
if(k) aux[i][j][k] += lef[k - 1];
if(k < SZ(gj)) aux[i][j][k] += rig[k];
}
}
}
for(int i = 1; i < (1 << g); i++) {
dp[i] = oo;
for(int j = 0; j < g; j++) {
if(i >> j & 1) {
int k = i ^ (1 << j);
int len = SZ(G[groups[j]]);
auto go = [&] (int pos) {
ll res = C2(pos) + C2(len - pos);
for(int l = 0; l < g; l++) if(k >> l & 1)
res += aux[l][j][pos] * 2;
return res;
};
int lb = 0, rb = len - 1;
while(lb <= rb) {
int mb = (lb + rb) / 2;
if(go(mb) > go(mb + 1)) lb = mb + 1;
else rb = mb - 1;
}
cmin(dp[i], dp[k] + go(lb));
}
}
}
ll ans = dp[(1 << g) - 1];
if(ans & 1) cout << ans / 2 << ".5\n";
else cout << ans / 2 << '\n';
}
