output_description: Print the minimum number of watering operations required to satisfy the
  condition.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N
      h_1 h_2 h_3 ...... h_N
attempt: import sys
  def LI(): return list(map(int, sys.stdin.buffer.readline().split()))
  def I(): return int(sys.stdin.buffer.readline())
  def LS(): return sys.stdin.buffer.readline().rstrip().decode('utf-8').split()
  def S(): return sys.stdin.buffer.readline().rstrip().decode('utf-8')
  def IR(n): return [I() for i in range(n)]
  def LIR(n): return [LI() for i in range(n)]
  def SR(n): return [S() for i in range(n)]
  def LSR(n): return [LS() for i in range(n)]
  def SRL(n): return [list(S()) for i in range(n)]
  def MSRL(n): return [[int(j) for j in list(S())] for i in range(n)]
  mod = 10 ** 9 + 7
  
  n = I()
  hl = LI()
  # count = 0
  
  # len_h = len(hl)
  
  # def m1(n):
  #     if n > 0:
  #         n = n - 1
  #     else:
  #         n = 0
  #     return n
  
  # max_hana = max(hl)
  # if max_hana == 0:
  #     print(0)
  #     sys.exit()
  
  # for i in range(max_hana):
  #     for j in range(len_h):
  #         if j == 0:
  #             if hl[j] > 0:
  #                 count += 1
  #         else:
  #             if hl[j] > 0 and hl[j-1] == 0:
  #                 count += 1
  #             elif hl[j] > 0 and hl[j-1] == 0:
  #                 count += 1
  #     hl = list(map(m1, hl))
  
  # print(count)
  
  ######################
  # 隣との差分を考えたほうが早い
  
  # 1    2    4    2    1    0      計4
  #   1    2    0    0     0
  
  ans = hl[0]
  for i in range(1, N)
      ans += max(0, hl[i] - hl[i - 1])
  print(ans)
  
  
problem_description: Statement
  
  In a flower bed, there are N flowers, numbered 1,2,......,N. Initially, the
  heights of all flowers are 0. You are given a sequence
  h=\\{h_1,h_2,h_3,......\\} as input. You would like to change the height of
  Flower k to h_k for all k (1 \leq k \leq N), by repeating the following
  "watering" operation:
  
    * Specify integers l and r. Increase the height of Flower x by 1 for all x such that l \leq x \leq r.
  
  Find the minimum number of watering operations required to satisfy the
  condition.
samples: [{"input": "4\n    1 2 2 1", "output": "2\n    \n\nThe minimum number of watering operations required is 2. One way to achieve it\nis:\n\n  * Perform the operation with (l,r)=(1,3).\n  * Perform the operation with (l,r)=(2,4).\n\n* * *"}, {"input": "5\n    3 1 2 3 1", "output": "5\n    \n\n* * *"}, {"input": "8\n    4 23 75 0 23 96 50 100", "output": "221"}]