#include #include #include #include #include #include #include #include #include #include #include #include #include #define debug_value(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << #x << "=" << x << endl; #define debug(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << x << endl; template inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; } template inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; } using namespace std; typedef long long ll; template vector> vec2d(int n, int m, T v){ return vector>(n, vector(m, v)); } template vector>> vec3d(int n, int m, int k, T v){ return vector>>(n, vector>(m, vector(k, v))); } template void print_vector(vector v, char delimiter=' '){ if(v.empty()) { cout << endl; return; } for(int i = 0; i+1 < v.size(); i++) cout << v[i] << delimiter; cout << v.back() << endl; } int main(){ ios::sync_with_stdio(false); cin.tie(0); cout << setprecision(10) << fixed; ll n, m; cin >> n >> m; if(n%2 == 0 && m%2 == 0){ cout << 0 << endl; return 0; } ll a = ((n+1)/2)*((m+1)/2); ll b = ((n+1)/2)*(m/2); ll c = (n/2)*((m+1)/2); ll d = (n/2)*(m/2); if(n%4 == 3 && m%4 == 3){ ll x = n*m-d*4; cout << x/4-1 << endl; }else{ ll x = n*m-d*4; cout << x/4 << endl; } }