#include <bits/stdc++.h>
using namespace std;
int main() {
  int64_t H, W;
  cin >> H >> W;
  if (H == 1 || W == 1) {
    cout << 1 << endl;
  } else {
    int64_t A = ((H + 1) / 2) * ((W + 1) / 2);
    int64_t B = (H / 2) * (W / 2);
    cout << A + B << endl;
  }
}
