output_description: Print the number of white cells that will remain.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      H W
      h w
attempt: x = input()
  y = x.split(" ")
  map = [int(i) for i in y]
  x = input()
  y = x.split(" ")
  cell = [int(i) for i in y]
  map[0] = map[0] - cell[0]
  map[1] = map[1] - cell[1]
  print(map[0] * map[1])
  
problem_description: Statement
  
  There are H rows and W columns of white square cells.
  
  You will choose h of the rows and w of the columns, and paint all of the cells
  contained in those rows or columns.
  
  How many white cells will remain?
  
  It can be proved that this count does not depend on what rows and columns are
  chosen.
samples: [{"input": "3 2\n    2 1", "output": "1\n    \n\nThere are 3 rows and 2 columns of cells. When two rows and one column are\nchosen and painted in black, there is always one white cell that remains.\n\n* * *"}, {"input": "5 5\n    2 3", "output": "6\n    \n\n* * *"}, {"input": "2 4\n    2 4", "output": "0"}]