#include <iostream>
#include <vector>
#include <cmath>

using namespace std;

int areaObjects(int n, int m) {
    if (n <= 0 || m <= 0) {
        return 0;
    }
    vector <float> a;
    int s=n*m;
    a.push_back(s);
    int i=1;
    int k=0;
    int t1;
    int t2;
    while (i-k!=0) {
      for (int j=k;j<i; j++){
        if (a[j]>1) {
          t1=ceil(a[j]/2);
          t2=floor(a[j]/2);
          a.push_back(t1);
          a.push_back(t2);
        //  cout<<t1<<" "<<t2<<" ";
      }
      }
      k=i;
      i=a.size();
    }
    long sum=0;
    for (int j=0;j<a.size(); j++){
      sum=sum+a[j];
    }
    
    

    return sum;
}

int main() {
    int n, m;
    cin>>n>>m;
    int result = areaObjects(n, m);
    cout << result << endl;
    return 0;
}