cuc

My grandma has a cuckoo clock that sings every hour (a number of times equal to the hour) and at "half past" (just once). Hours on my grandma's clock are numbered from 1 to 12. I left home exactly after the cuckoo sang an hour and I was gone at least one hour. After I came back the cuckoo sang "half past" and grandma turned to me upset and said: „Ever since you left the cuckoo sang x times!"

Task

Because I can't understand why my grandma's so upset write a program that determines the minimum number of hours I was gone!

Input

Input file cuc.in contains on the first line the positive integer x.

Output

Output file cuc.out must contain only one line with a positive integer that represents the minimal number of hours I was gone from home.

Constraints

Example
cuc.in cuc.out Explanation
18

3

I was out 3 hours, from 3 to 6 (I left home after the cuckoo sang for 3 o'clock and I returned before the cuckoo sang for 6.30).
Another solution would have been for me to have been gone 4 hours, from 1 to 5 but this is not the minimal solution.

Time limit: 0.1 seconds/test

prof. Emanuela Cerchez
 Computer Science High School "Grigore Moisil"Iasi
 Contact:emanuela.cerchez@gmail.com