jmc

After doing so twice, he gets $25$. He then divides $25$ by $2$ to get $12.5$, and then takes the greatest integer to get $12$. He now divides by $2$ twice to get $3$. Finally, he divides by $2$ to get $1.5$ and takes the greatest integer to get $1$. This is a total of $\boxed{6}$ times.