1.
Let [x][x] denote the greatest integer x\le x, where xRx\in\mathbb{R}. If the domain of the real valued function f(x)=[x]2[x]3f(x)=\sqrt{\frac{|[x]|-2}{|[x]|-3}} is (,a)[b,c)[4,)(-\infty, a)\cup[b,c)\cup[4,\infty), a<b<ca<b<c, then the value of a+b+ca+b+c is: