// This is free and unencumbered software released into the public domain. // Anyone is free to copy, modify, publish, use, compile, sell, or // distribute this software, either in source code form or as a compiled // binary, for any purpose, commercial or non-commercial, and by any // means. // In jurisdictions that recognize copyright laws, the author or authors // of this software dedicate any and all copyright interest in the // software to the public domain. We make this dedication for the benefit // of the public at large and to the detriment of our heirs and // successors. We intend this dedication to be an overt act of // relinquishment in perpetuity of all present and future rights to this // software under copyright law. // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. // IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR // OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, // ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR // OTHER DEALINGS IN THE SOFTWARE. // For more information, please refer to /****************/ /* template.hpp */ /****************/ #include #include #include #include #include #include using std::cerr; using std::cout; using std::endl; using std::max; using std::min; using std::swap; struct BoolName : std::numpunct { std::string t, f; BoolName(std::string t, std::string f) : t(t), f(f) {} std::string do_truename() const { return t; } std::string do_falsename() const { return f; } }; void setBoolName(std::string t, std::string f) { cout.imbue(std::locale(cout.getloc(), new BoolName(t, f))); } struct Initializer { Initializer() { cout << std::fixed << std::setprecision(15) << std::boolalpha; setBoolName("Yes", "No"); } } initializer; struct Input { bool eof; Input() : eof(false) {} operator char() { char v; this->eof = (std::scanf("%c", &v) != 1); return v; } operator int() { int v; this->eof = (std::scanf("%d", &v) != 1); return v; } operator long() { long v; this->eof = (std::scanf("%ld", &v) != 1); return v; } operator long long() { long long v; this->eof = (std::scanf("%lld", &v) != 1); return v; } operator unsigned int() { unsigned int v; this->eof = (std::scanf("%u", &v) != 1); return v; } operator unsigned long() { unsigned long v; this->eof = (std::scanf("%lu", &v) != 1); return v; } operator unsigned long long() { unsigned long long v; this->eof = (std::scanf("%llu", &v) != 1); return v; } operator double() { double v; this->eof = (std::scanf("%lf", &v) != 1); return v; } operator long double() { long double v; this->eof = (std::scanf("%Lf", &v) != 1); return v; } void ignore() const { getchar(); } } in; template T abs(T a) { return a >= 0 ? a : -a; } template bool chmin(T &a, const S &b) { return a > b ? a = b, true : false; } template bool chmax(T &a, const S &b) { return a < b ? a = b, true : false; } template std::function cast() { return [](const T &t) { return static_cast(t); }; } template T copy(const T &a) { return T(a); } class ZeroPadding { public: ZeroPadding(int n) : n(n) {} int n; }; std::ostream &operator<<(std::ostream &os, const ZeroPadding &z) { os << std::setw(z.n) << std::setfill('0'); return os; } template constexpr T inf() { return std::numeric_limits::max() / 2 - 1; } /************/ /* main.cpp */ /************/ int main() { int64_t r(in), c(in); cout << r * c / (r == c ? 4 : 2) - (r * c % 2 ? 0 : 1) << endl; }