import re
import sys

content = input()
pattern = r'^(\d+)$'
result = re.match(pattern, content)

if not result:
    sys.exit("format error.")

N = int(content)

if not (2 <= N and N <= 2*10**5):
     sys.exit("N")


content = input()
pattern = r'^([<>]{' + str(N-1) + r'})$'
result = re.match(pattern, content)

if not result:
    sys.exit("format error.")

print("OK")