题目描述

The basic task is simple: given $N$ real numbers, you are supposed to calculate their average. But what makes it complicated is that some of the input numbers might not be legal. A legal input is a real number in$[−1000,1000]$ and is accurate up to no more than $2$ decimal places. When you calculate the average, those illegal numbers must not be counted in.

输入格式

Each input file contains one test case. For each case, the first line gives a positive integer $N$ ($N$≤100). Then N numbers are given in the next line, separated by one space.

It is guaranteed that all the lengths of the numbers are within 100.

输出格式

For each illegal input number, print in a line ERROR: X is not a legal number where X is the input. Then finally print in a line the result: The average of K numbers is Y where K is the number of legal inputs and Y is their average, accurate to 2 decimal places. In case the average cannot be calculated, output Undefined instead of Y. In case K is only 1, output The average of 1 number is Y instead.

样例

7 
5 -3.2 aaa 9999 2.3.4 7.123 2.35

ERROR: aaa is not a legal number 
ERROR: 9999 is not a legal number 
ERROR: 2.3.4 is not a legal number 
ERROR: 7.123 is not a legal number 
The average of 3 numbers is 1.38 

2 
aaa -9999

ERROR: aaa is not a legal number 
ERROR: -9999 is not a legal number 
The average of 0 numbers is Undefined