题解与来源题共享。已有题解默认通过；新增或编辑后需由来源域管理员审核。待审核、驳回题解仅作者和审核管理员可见。来源域：system

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  li1005345206 LV 6 @ 2026-5-11 20:15:55

  
  
  import os
  import sys
  input = lambda:sys.stdin.readline().strip()
  minput = lambda:map(int, input().split())
  n = int(input())
  a = minput()
  prev = 1
  d = []
  for i in a:
      d.append(i - prev)
      prev = i
  r = 0
  t = [i for i in d if i > 0]
  print(sum(t))