#include<stdio.h>
int main()
{
int a,b;
int res=0;
scanf("%d %d",&a,&b);
res = ((a/2)*(b/3)+(a/3)*(b/2))*2;
printf("%d",res);
return 0;
}
#include<stdio.h>
int main()
{
int a,b;
int res=0;
scanf("%d %d",&a,&b);
res = ((a/2)*(b/3)+(a/3)*(b/2))*2;
printf("%d",res);
return 0;
}