Again Help Chapter 2

[BloodyHash]

So let me show a demo

HP= 0
PRINT " A MONSTER APPEARD"
PRINT
PRINT (1) GERMAN SUPLEX
INPUT X
IF X = 1 THEN HP = 0

what i want is if people press other then 1 i wanna put "ERROR" and then put back to PRINT (1) GERMAN SUPLEX