LC3 Program to echo user entered characters

I need a program to echo the user entered strings. I have write this code. but its not working properly. Please help me out.

			.ORIG x3000 
			LEA		R0, Message ; display a message
			PUTS
			LEA		R1, FirstChar ; R1 points to the first
						  ; character which will be entered

; the loop for echoing user's input 
Next	LD	R2, LF_ASCII															 
		GETC				; read in one character 
		OUT					; write character entered
		ADD	R3, R1, 1			; R3 points to the next character
		ADD	R4, R0,	R2		; check whether the input is LF
		BRnp	Next			; if input is LF check whether it's,
								

Message  .STRINGZ	"Please enter a string: "
LF_ASCII	.FILL		-10 
FirstChar	.BLKW		10

		.END