ACMSGURU 105  Div 3
Div 3
Problem Description
There is sequence 1, 12, 123, 1234, …, 12345678910, … . Given first N elements of that sequence. You must determine amount of numbers in it that are divisible by 3.
Input
Input contains N (1<=N<=2^31  1).
Output
Write answer to the output.
Sample Input
4
Sample Output
2
Solution
1 
