def random_walk(data):
	i = 1
	t = 0
	for i in range(len(data) - 1):
		if data[i] + 1 == data[i + 1] or data[i] - 1 == data[i + 1]:
			t = t + 1
	

	if t == len(data) - 2 and data[1] != 0:
		print("T")
	else:
		print("F")
		
			
data1 = [3, 1, 2, 1]
data2 = [5, -1, -2, 0, 1, 2]
data3 = [4, 0, 1, 2, 1]

random_walk(data1)
random_walk(data2)
random_walk(data3)