n,d=map(int,input().split())
a=[int(x) for x in input().split()]
share=True 
buy=a[0]
profit=0
for i in range(0,n):
  if share:
    if a[i]>=buy+d:
      profit += a[i]-buy
      sale=a[i]
      share=False 
  else:
    if a[i]<=sale-d:
      buy=a[i]
      share=True 
print(profit)