A reinforced concrete beam with rectangular cross section (width = $300$ $\text{mm}$, effective depth = $580$ $\text{mm}$) is made of $M30$ grade concrete. It has $1\%$ longitudinal tension reinforcement of $\text{Fe}$ $415$ grade steel. The design shear strength for this beam is $0.66\: N/mm^{2}$. The beam has to resist a factored shear force of $440$ $\text{kN}$. The spacing of two-legged, $10$ $\text{mm}$ diameter vertical stirrups of $\text{Fe}$ $415$ grade steel is ____________ $\text{mm}$. *(round off to the nearest integer)*