The total primary consolidation settlement $\left(S_{c}\right)$ of a building constructed on a $10 \mathrm{~m}$ thick saturated clay layer is estimated to be $50 \mathrm{~mm}$. After $300$ days of the construction of the building, primary consolidation settlement was reported as $10 \mathrm{~mm}$. The additional time (in days) required to achieve $50 \%$ of $S_{c}$ will be $\_\_\_\_\_\_\_$ (rounded off to the nearest integer).