import sys


def main():
	lines = sys.stdin.readlines()

	n_str = lines[0].rstrip('\n')
	n = int(n_str)

	assert 1 <= n <= 100
	assert str(n) == n_str
	assert len(lines) == n + 1

	for i in range(n):
		line = lines[i + 1].rstrip('\n')
		a, b = tuple(map(int, line.split()))

		assert 1 <= a <= 10**3
		assert 1 <= b <= 10**3
		assert ' '.join(map(str, (a, b))) == line

	print('OK')


if __name__ == '__main__':
	main()