Tanning Salon

Tan Your Hide, Inc. owns several coin-operated tanning salons. Research has shown that if a customer arrives and there are no beds available, the customer will turn around and leave, costing the company a sale. Write a program that tells the company how many customers left without tanning.

The input consists of data for one or more salons, followed by a line containing the number 0 that signals the end of the input. Data for each salon is a single line containing a positive integer that represents the number of tanning beds in the salon, followed by a space, followed by a sequence of uppercase letters. Letters in the sequence occur in pairs: the first occurrence of a letter indicates the arrival of a customer, and the second occurrence indicates the departure of that same customer. No letter occurs in more than one pair. Customers who leave without tanning always depart before customers who are currently tanning. There are at most 20 beds per salon.

For each salon, output on its own line a single sentence telling how many customers, if any, walked away, using exactly the format below. If no customer walked away, print All customers tanned successfully. Otherwise, letting $k$ be the number of customers who walked away, print k customer(s) walked away. (for example, 2 customer(s) walked away. when two customers left).