URI Online Judge | 1154

Ages

Adapted by Neilor Tonin, URI Brazil

Timelimit: 1

Write an algorithm to read an undeterminated number of data, each containing an individual's age. The final data, which will not enter in the calculations, contains the value of a negative age. Calculate and print the average age of this group of individuals.

Input

The input contains an undetermined number of integers. The input will be stop when a negative value is read.

Output

The output contains a value corresponding to the average age of individuals.

The average should be printed with two digits after the decimal point.

Input Sample Output Sample

34
56
44
23
-2

39.25