n,s,k=map(int,input().split())
ansd=-1
ansno=-1
for i in range(1,n+1):
	d=abs(s-int(input()))
	if d<=k:
		if ansd==-1 or d<ansd:
			ansd=d
			ansno=i
if ansno==-1:
	print("Unlucky!")
else:
	print(ansno)