Sum 3

Write a Python script that repeatedly asks the user to input even numbers and sums them until the user enters a “.” as input. Then, the sum is printed. The script should check whether the input is an even number. If the input is not an even number, print “Error, that is not an even number,” and prompt for a new input.

At the beginning of the script, display the message: “End input with a .”.

Example

Input

2
2
.

Output

4