#include<cstdio>
#include<algorithm>
using namespace std;
int main()
{
#ifdef local
	freopen("pro.in","r",stdin);
#endif
	int n,m;
	scanf("%d%d",&n,&m);
	if(n>m) swap(n,m);
	if(n==1) printf("%d",(m/6*3+max(m%6-3,0))*2);
	else if(n==2) printf("%d",m==2?0:m==3?4:m==7?12:m*2);
	else printf("%lld",1LL*n*m/2*2);
	return 0; 
}