4. Air purification devices in the room clean the air. The airflow over time for the first device changes according to the formula $f(t)=2^{t}$, and for the second device, it is $f(t)=2^{t+3}$. In the room, there are four devices of the first type and one of the second type. $S$ how many purification devices with a flow rate of $f(t)=2^{t+2}$ could replace the existing ones?