#include #ifdef _DEBUG #include "../../../debug_print.hpp" #else #define debug(...) #endif #define sort_(a) sort(a.begin(), a.end()) #define rsort(a) sort(a.rbegin(), a.rend()) #define rep(i, n) for (int i = 0; i < n; i++) #define rrep(i, n) for (int i = n - 1; 0 <= i; i--) #define for_(i, start, end) for (int i = start; i < end; i++) #define rfor(i, start, end) for (int i = start - 1; 0 <= i; i--) #define all(a) a.begin(), a.end() using ll = long long; using ld = long double; using namespace std; constexpr int INF32 = 1'050'000'000; constexpr long long INF64 = 4'000'000'000'000'000'000; constexpr int MOD7 = 1'000'000'007; constexpr int MOD53 = 998'244'353; constexpr double PI = 3.14159265358979323846; template inline bool chmin(T &a, T b) { if (a > b) { a = b; return true; } return false; } template inline bool chmax(T &a, T b) { if (a < b) { a = b; return true; } return false; } void print() { std::cout << '\n'; } template void print(H &&head, T &&... args) { std::cout << head; sizeof...(args) == 0 ? std::cout << "" : std::cout << ' '; print(std::forward(args)...); } template void print(std::vector &v) { for (int i = 0; i < v.size(); i++) { std::cout << v[i]; i == v.size() - 1 ? std::cout << '\n' : std::cout << ' '; } } template void print(std::vector> &v) { for (int i = 0; i < v.size(); i++) { for (int j = 0; j < v[i].size(); j++) { std::cout << v[i][j]; j == v[i].size() - 1 ? std::cout << '\n' : std::cout << ' '; } } } void scan() {} template void scan(H &&head, T &&... args) { std::cin >> head; scan(std::forward(args)...); } template void scan(std::vector &v) { for (auto &&i : v) { scan(i); } } int main() { cin.tie(0); ios::sync_with_stdio(false); int L, K; scan(L, K); K *= 2; int ans = L / K == 1 ? 0 : L / K * K / 2; print(ans); return 0; }