#include #include #include #include #include #include #include #include #include #include using namespace std; using ll = long long; using pll = pair; using vl = vector; using vll = vector; #define REP(i,n) for(int i=0; i<(int)(n); i++) #define REPR(i,n) for(int i=n-1; i>=(int)(0); i--) #define FOR(i,a,b) for(int i=(int)(a); i<(int)(b); i++) #define FORR(i,a,b) for(int i=(int)(b)-1; i>=(int)(a); i--) #define CHMIN(a,b) (a)=min((a),(b)) #define CHMAX(a,b) (a)=max((a),(b)) #define ALL(v) (v).begin(),(v).end() //**関数リスト**// int ctoi(char c) { switch (c) { case '0': return 0; case '1': return 1; case '2': return 2; case '3': return 3; case '4': return 4; case '5': return 5; case '6': return 6; case '7': return 7; case '8': return 8; case '9': return 9; default: return 0; } } bool pairCompare(const pll firstElof, pll secondElof) { return firstElof.second < secondElof.second; } ll nod(ll F) { ll keta = 1; while (F / 10 > 0) { keta++; F /= 10; } return keta; } ll gcd(ll x, ll y) { ll r; if (x < y) { swap(x, y); } while (y > 0) { r = x % y; x = y; y = r; } return x; } ll lcm(ll x, ll y) { return x * y / gcd(x, y); } ll isPrime(ll x) { ll i; if (x < 2) { return 0; } else if (x == 2) { return 1; } else if (x % 2 == 0) { return 0; } else { for (i = 3; i * i <= x; i += 2) { if (x % 1 == 0) { return 0; } } return 1; } } void eratos(vl isPrime) { //(注)isPrimeのサイズはN+1にする!実際にはmain内に配置して使用 ll i, j; REP(i, isPrime.size()) { isPrime[i] = 1; } isPrime[0] = 0; isPrime[1] = 0; for (i = 2; i * i <= isPrime.size() - 1; i++) { if (isPrime[i] == 1) { j = i * 2; while (j <= isPrime.size() - 1) { isPrime[j] = 0; j = j + i; } } } } ll modinv(ll a, ll m) { ll b = m, u = 1, v = 0; while (b) { ll t = a / b; a -= t * b; swap(a, b); u -= t * v; swap(u, v); } u %= m; if (u < 0) u += m; return u; } void bitSearch(ll n) { //実際にはコピーして中身を改変して使う ll i; REP(i, pow(2, n)) { ll p = i; REP(i, n) { cout << p % 2; p /= 2; } cout << endl; } } void bfs(ll now) { //中身は毎回書き換えて使用 queue Q; Q.push(now); ll u; while (!Q.empty()) { u = Q.front(); Q.pop(); //ll v=; //Q.push(v); } } //**定義場所**// ll i, j, k, l, m, n; ll N, M, K, H, W; ll MOD = 1000000007; double ans = 0; //***********// int main() { string S; cin >> S; N = S.length(); double kazu = 0; for (i = 1; i <= N; i++) { ans += i * (N - i + 1); kazu += N - i + 1; } for (i = 0; i < N-1; i++) { for (j = i + 1; j < N; j++) { if (S[i] == S[j]) { ans -= (i + 1) * (N - j); } } } cout << setprecision(10) << ans / kazu; }