N recruits are standing in front of a sergeant who orders to turn left. Some of the soldiers turn left, while the others turn right. In a second each recruit seeing the face of another recruit understands that a mistake was made and turns around. This happens at the same time to each pair of soldiers facing each other. The process continues until the formation becomes stable. Write a program, which finds out the number of times when a pair of soldiers turned around. If the process is infinite then the program should write the word “NO”.

Example:
Legend:
‘<’: a recruit facing left;
‘>’: a recruit facing right.

Formation	Comments	Number of turns
> > < < > <	Initial formation	2
> < > < < >	One second has passed	2
< > < > < >	Two seconds have passed	2
< < > < > >	Three seconds have passed	1
< < < > > >	Final formation	Total: 7

The first line contains the number of recruits (N). The rest of the input contains only ‘<’, ‘>’ and line break characters. There is exactly N ‘<’ and ‘>’ characters in the input. Each line of the input may have up to 255 characters.
1 ≤ N ≤ 30000.

Write the number of turns.