output_description: Print the area of the triangle ABC.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      |AB| |BC| |CA|
attempt: n = int(input())
  h = list(map(int, input().split()))
  sum = 0
  for i in range(max(h)):
      if 0 not in h:
          h = [i - 1 if i > 0 else 0 for i in h]
          sum += 1
          # print(h,1)
      else:
          count0 = [i for i, j in enumerate(h) if j == 0]
          a = count0.copy()  # copy()をつけないとaを変えるとcount0も変わる
          b = count0.copy()
          a.pop(0)
          b.pop(-1)
          c = [x - y for (x, y) in zip(a, b)]  # a-bが要素のリストを作る
          sum = sum + len(c) - c.count(1)
          # print(count0)
          if count0[0] > 0 and count0[-1] < n - 1:
              sum += 2
              # print(1)
          elif count0[0] > 0 or count0[-1] < n - 1:
              sum += 1
              # print(2)
          else:
              sum += 0
          h = [i - 1 if i > 0 else 0 for i in h]
          # print(h,2)
  print(sum)
  
problem_description: Statement
  
  There is a right triangle ABC with ∠ABC=90°.
  
  Given the lengths of the three sides, |AB|,|BC| and |CA|, find the area of the
  right triangle ABC.
  
  It is guaranteed that the area of the triangle ABC is an integer.
samples: [{"input": "3 4 5", "output": "6\n    \n\n![tri](https://img.atcoder.jp/ghi/44c1d4cbdf4677ce3b08ca70b5ce98ea.png)\n\nThis triangle has an area of 6.\n\n* * *"}, {"input": "5 12 13", "output": "30\n    \n\nThis triangle has an area of 30.\n\n* * *"}, {"input": "45 28 53", "output": "630\n    \n\nThis triangle has an area of 630."}]