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