The stepwise formation of $\left[\mathrm{Cu}\left(\mathrm{NH}_3\right)_4\right]^{2+}$ is given below
$
\begin{aligned}
& \mathrm{Cu}^{2+}+\mathrm{NH}_3 \underset{1}{\stackrel{\mathrm{~K}_1}{\rightleftharpoons}}\left[\mathrm{Cu}\left(\mathrm{NH}_3\right)\right]^{2+} \\
& {\left[\mathrm{Cu}\left(\mathrm{NH}_3\right)\right]^{2+}+\mathrm{NH}_3 \underset{2}{\stackrel{K_2}{\rightleftharpoons}}\left[\mathrm{Cu}\left(\mathrm{NH}_3\right)_2\right]^{2+}} \\
& {\left[\mathrm{Cu}\left(\mathrm{NH}_3\right)_2\right]^{2+}+\mathrm{NH}_3 \underset{2}{\stackrel{K_3}{\rightleftharpoons}}\left[\mathrm{Cu}\left(\mathrm{NH}_3\right)_3\right]^{2+}} \\
& {\left[\mathrm{Cu}\left(\mathrm{NH}_3\right)_3\right]^{2+}+\mathrm{NH}_3 \underset{4}{\stackrel{K_4}{\rightleftharpoons}}\left[\mathrm{Cu}\left(\mathrm{NH}_3\right)_4\right]^{2+}}
\end{aligned}
$
The value of stability constants $\mathrm{K}_1, \mathrm{~K}_2, \mathrm{~K}_3$ and $\mathrm{K}_4$ are $10^4, 1.58 \times 10^3, 5 \times 10^2$ and $10^2$ respectively. The overall equilibrium constants for dissociation of $\left[\mathrm{Cu}\left(\mathrm{NH}_3\right)_4\right]^{2+}$ is $\mathrm{x} \times 10^{-12}$. The value of x is $\_\_\_\_$ . (Rounded off to the nearest integer)
