day=0
n,k=map(int,input().split())
sales=list(map(int,input().split()))
days=[]
for a in range(len(sales)):
day=0
for b in range(len(sales)):
day=b+1
if b>=a:
if sales[b]>=sales[a]+k:
days.append(day)
break
if day==len(sales):
days.append(-1)
day+=1
print(days)