ITC reversal

hi ,I have a query regarding itc reversal if payment is not made to supplier under 180 day,
let suppose I purchase goods of 100 rs and gst rate is 5% and availed credit in that particular month and paid the 50 % amount ie 52.5 in same month but unable to pay the rest 50 % within 180 day. My question is how much I need to reverse itc