Problem Statement
Write a program that counts how many numbers from 1 to N (inclusive) are divisible by both 3 and 5.
A number is divisible by both 3 and 5 if and only if it is divisible by 15. For example, between 1 and 30, the numbers divisible by both 3 and 5 are: 15 and 30, so the count is 2.
Your program should read a single integer N and output the count of numbers divisible by both 3 and 5 in the range [1, N].