#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define X first #define Y second #define pb push_back #define rep(X,Y) for (int (X) = 0;(X) < (Y);++(X)) #define reps(X,S,Y) for (int (X) = S;(X) < (Y);++(X)) #define rrep(X,Y) for (int (X) = (Y)-1;(X) >=0;--(X)) #define rreps(X,S,Y) for (int (X) = (Y)-1;(X) >= (S);--(X)) #define repe(X,Y) for ((X) = 0;(X) < (Y);++(X)) #define peat(X,Y) for (;(X) < (Y);++(X)) #define all(X) (X).begin(),(X).end() #define rall(X) (X).rbegin(),(X).rend() #define eb emplace_back #define UNIQUE(X) (X).erase(unique(all(X)),(X).end()) #define Endl endl using namespace std; typedef long long ll; typedef pair pii; typedef pair pll; template using vv=vector>; template ostream& operator<<(ostream &os, const vector &t) { os<<"{"; rep(i,t.size()) {os< ostream& operator<<(ostream &os, const pair &t) { return os<<"("< inline bool MX(T &l,const T &r){return l inline bool MN(T &l,const T &r){return l>r?l=r,1:0;} #define out(args...){vector a_r_g_s=s_p_l_i_t(#args, ','); e_r_r(a_r_g_s.begin(), args); } vector s_p_l_i_t(const string &s, char c){vector v;int d=0,f=0;string t;for(char c:s){if(!d&&c==',')v.pb(t),t="";else t+=c;if(c=='\"'||c=='\'')f^=1;if(!f&&c=='(')++d;if(!f&&c==')')--d;}v.pb(t);return move(v);} void e_r_r(vector::iterator it) {} template void e_r_r(vector::iterator it, T a, Args... args){ if(*it==" 1"||*it=="1") cerr< substr((*it)[0] == ' ', it -> length()) << " = " << a << ", "; e_r_r(++it, args...);} const ll MOD=1e9+7; int main(){ ios_base::sync_with_stdio(false); cout<>n>>m; if(m%2) swap(n,m); assert(m%2==0); if(n%2){ cout<<(n+1)/2*2*m+n/2<