For any increasing sequence of real numbers $a_1,a_2,a_3,\mathrm{...}$ let us denote A as $\prec \prec a_1,a_2,a_3,a_4,\mathrm{...}\succ \succ ,$ and a sequence $\Delta A$ is defined as $\prec \prec a_2-a_1,a_3-a_2,a_4-a_3,\mathrm{.......}\succ \succ .$ Suppose that all of the terms of the sequence $\Delta \left(\Delta A\right)$ are 1 and that $a_{19}=a_{92}=0.$ Then the sum of digit(s) of $a_3$ is M, then the value of $\left[\frac{M}{2}\right]$ is ____, where $[.]$ is greatest integer function.