1246 : Phone numbers

Phone number in Berland is a sequence of n digits. Often, to make it easier to memorize the number, it is divided into groups of three digits. For example, the phone number 119733 is easier to remember as 119-733. Your task is to find for a given phone number divisions into groups of three digits. 

N cases,Each case the first line contains integer n (3 ≤ n ≤ 100) (n is a multiple of 3 

)— amount of digits in the phone number. The second line contains n digits — the phone number to divide into groups. 

Output divisions of the given phone number into groups of three digits. Separate groups by single character -. 

2
6
549871
3
117

549-871
117