A prismatic fixed-fixed beam, modelled with a total lumped-mass of $\text{10 kg}$ as a single degree of freedom $\text{(SDOF)}$ system is shown in the figure.

If the flexural stiffness of the beam is $4 \pi ^{2}$ $\text{kN/m}$, its natural frequency of vibration (in $\text{Hz}$, $\textit{in integer}$) in the flexural mode will be ______________