using namespace std;
#include <bits/stdc++.h>

int main(){
	int A,B;
	int AS;
	cin >> A >> B;
	if (A%2==0){
		AS = A / 2;
	  cout << AS*B << endl;	
	}else{
		AS = A % 2;
		cout << AS+B << endl;
	}
}