KPSUM  The Sum
One of your friends wrote numbers 1, 2, 3, ..., N on the sheet of paper. After that he placed signs + and  between every pair of adjacent digits alternately. Now he wants to find the value of the expression he has made. Help him.
For example, if N=12 then
+1 2 +3 4 +5 6 +7 8 +9 1+0 1+1 1+2 = 5
Input
Each line contains one integer number N (1≤ N ≤ 10^{15}). Last line contains 0 and shouldn't be processed. Number of lines in the input does not exceed 40.
Output
For every line in the input write the answer on a separate line.
Example
Input: 12 0 Output: 5
hide comments
abdou_93:
20131118 02:57:49
@The new guy.. yes the ans for 10^15


Sandeep Pathry:
20130531 06:31:38
Last edit: 20130531 06:55:30 

The new guy:
20120109 12:12:43
Is the ans for 10^15 = 409090909090909 ?? Please help someone!! 
Added by:  Pavel Kuznetsov 
Date:  20070326 
Time limit:  0.114s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: ERL JSRHINO NODEJS PERL6 VB.NET 
Resource:  Vologda 2007 