#include <bits/stdc++.h>
using namespace std;
int main() {
  int H, W, ans;
  cin >> H >> W;
  if (H == 1 || W == 1) {
    cout << 1 << endl;
    return 0;
  }
  if (H % 2 == 0)
    ans = H / 2 * W;
  else
    ans = (H / 2 + 1) * W - W / 2;
  cout << ans << endl;
  return 0;
}
