For every "X" amount, do "Y"

I'm sure this has a simple answer I'm overlooking, but how can I calculate something based on the following situation?

Cell A1 contains a variable number.
Cell A2 contains a set number.
Cell A3 contains a formula that multiplies A2 at certain intervals.

Lets say the interval is 5. In essence, the following would happen.

When A1=0-4, A3 does nothing.
When A1=5-9, A3 multiplies A2 by 1.
When A1=10-14, A3 multiplies A2 by 2.
When A1=15-19, A3 multiplies A2 by 3.
etc.

Hence the "interval" is 5, and the function increases the multiplication amount by a factor of 1 for each "interval".

= A2 * Int ( A /5)

Wow, fast response! I knew it was something easy...

Thank you!