a trainer in an athletic department was asked to arrange the towels in the locker room in stacks of equal size. When she separated the towels into stacks of 4, one was left over. When she tried stacks of 5, one was left over. The same was true for stacks of 6. However, she was successful in arranging the towels in stacks of 7 each. What is the smallest possible number of towels in the locker room?