#include using namespace std; typedef long long ll; #define F first #define S second #define pii pair #define eb emplace_back #define all(v) v.begin(), v.end() #define rep(i, n) for (int i = 0; i < (n); ++i) #define rep3(i, l, n) for (int i = l; i < (n); ++i) #define sz(v) (int)v.size() #define endl '\n' const int inf = 1000000007; const ll INF = 1e18; // int mod = 998244353; int mod = 1000000007; #define abs(x) (x >= 0 ? x : -(x)) #define lb(v, x) (int)(lower_bound(all(v), x) - v.begin()) #define ub(v, x) (int)(upper_bound(all(v), x) - v.begin()) template inline bool chmin(T1 &a, T2 b) { if (a > b) { a = b; return 1; } return 0; } template inline bool chmax(T1 &a, T2 b) { if (a < b) { a = b; return 1; } return 0; } ll gcd(ll a, ll b) { if (b == 0) return a; return gcd(b, a % b); } ll lcm(ll a, ll b) { return a / gcd(a, b) * b; } ll pow(ll a, int b) { return b ? pow(a * a, b / 2) * (b % 2 ? a : 1) : 1; } ll modpow(ll a, ll b, ll _mod) { return b ? modpow(a * a % _mod, b / 2, _mod) * (b % 2 ? a : 1) % _mod : 1; } template ostream& operator << (ostream& os, const pair& p) { os << p.F << " " << p.S; return os; } template ostream& operator << (ostream& os, const vector& vec) { rep(i, sz(vec)) { if (i) os << " "; os << vec[i]; } return os; } template inline istream& operator >> (istream& is, vector& v) { rep(j, sz(v)) is >> v[j]; return is; } template inline void add(T &a, T2 b) { a += b; if (a >= mod) a -= mod; } void solve(); int main() { ios::sync_with_stdio(false); cin.tie(0); cout.tie(0); cout << fixed << setprecision(10); int T; // cin >> T; T = 1; while (T--) { solve(); } } void solve() { int n, k; cin >> n >> k; cout << 1.0 * n * (n + 1) / 2 * k / (n + 1) / k << endl; }