// わからん

ll solve(ll X, ll Y){
  if(X==0 && Y==0) return 0;
  if(X==0 || Y==0) return 1;

  if(X==Y && X%2==0) return (X+1) * (Y+1) - max(X,Y) - 1;
  if(X%2==0 && Y%2==0) return (X+1) * (Y+1) - max(X,Y);
  if(X%2==1 && Y%2==1) return (X+1) * (Y+1) - min(X,Y);
  if(X%2==0) swap(X, Y);
  return (X+1) * (Y+1) - X;
}
{
  ll X, Y, r;
  rd(X, Y);
  r = solve(X, Y);
  wt(r);
}