def main(buffer, command):
	if len(command) == 2 and (command[1].isdigit() or command[1] in {"^","$"}):
		if command[1].isdigit():
			dot = int(command[1])
		elif command[1] == "^":
			dot = buffer.carat()
		elif command[1] == "$":
			dot = buffer.dollar()
	elif len(command) == 3 and command[1] in {"+","-"} and command[2].isdigit():
		if command[1] == "+":
			dot = buffer.dot + int(command[2])
		elif command[1] == "-":
			dot = buffer.dot - int(command[2])

	if not("dot" in locals()) or dot < buffer.carat() or dot > buffer.dollar():
		print("?")
	else:
		buffer.dot = dot

	return buffer