Problem - 50A - Codeforces

#include<bits/stdc++.h>
using namespace std;
const int N=1e5+5;
int n,m,res;
signed main(){
	scanf("%d%d",&n,&m);
	if(n>1){
		res+=n/2*m;
		n%=2;	
	}
	if(n==1) res+=m/2;
	cout<<res;
	return 0;
}