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