说明

Larry graduated this year and finally has a job. He's making a lot of money, but somehow never seems to have enough. Larry has decided that he needs to grab hold of his financial portfolio and solve his financing problems. The first step is to figure out what's been going on with his money. Larry has his bank account statements and wants to see how much money he has. Help Larry by writing a program to take his closing balance from each of the past twelve months and calculate his average account balance.

输入格式

Each case will be twelve lines. Each line will contain the closing balance of his bank account for a particular month. Each number will be positive and displayed to the penny. No dollar sign will be included.

输出格式

For each case, the output will be a single number, the average (mean) of the closing balances for the twelve months. It will be rounded to the nearest penny, preceded immediately by a dollar sign, and followed by the end-of-line. There will be no other spaces or characters in the output.

样例

2.68

5.1

68.4

3.66

2.36

3.14

3.48

48.3

168.1478

10256.1

12684.12

21.418

$1938.91

提示

翻译：
帮助拉里写一个程序由过去十二个月，每月他的期末余额，计算其平均帐户余额。 
输入
十二行。每一行都将包含一个特定的月份，他的银行账户的期末余额。每个数字都将是正的，显示精确到分钱。没有美元符号
输出
将是一个单独的数字，为十二个月的平均余额。这将是四舍五入到最接近的货币，数字前面有一个美元符号。 
思路：定义一个十二位数组a，输入十二个月份的月末余额存入a，将它们相加，后除以12，输出结果（平均余额）