output_description: Print the area of this yard excluding the roads (in square yards).
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      A B
attempt: # 二次元累積和
  # A[i1, j1] から A[i2, j2] までの長方形の積算値は
  # Acum[i2 + 1][j2 + 1] - Acum[i1][j2 + 1] - Acum[i2 + 1][j1] + Acum[i1][j1]
  def two_dim_accumulate(a) -> list:
      h, w = len(a), len(a[0])
      acum = [[0 for _ in range(w + 1)] for _ in range(h + 1)]
      for i in range(h):
          for j in range(w):
              acum[i + 1][j + 1] = a[i][j]
      for i in range(1, h + 1):
          for j in range(1, w + 1):
              acum[i][j] += acum[i][j - 1]
      for j in range(1, w + 1):
          for i in range(1, h + 1):
              acum[i][j] += acum[i - 1][j]
      return acum
  
  
  Acum = two_dim_accumulate(A)
  # for a in Acum:
  #  print(a)
  
problem_description: Statement
  
  There is a farm whose length and width are A yard and B yard, respectively. A
  farmer, John, made a vertical road and a horizontal road inside the farm from
  one border to another, as shown below: (The gray part represents the roads.)
  
  ![ ](https://img.atcoder.jp/ghi/27d063746b460f1132b6a99aa535a562.png)
  
  What is the area of this yard excluding the roads? Find it.
samples: [{"input": "2 2", "output": "1\n    \n\nIn this case, the area is 1 square yard.\n\n* * *"}, {"input": "5 7", "output": "24\n    \n\nIn this case, the area is 24 square yards."}]