output_description: Print the number of sand in the upper bulb after t second.
  
  * * *
input_description: The input is given from Standard Input in the following format:
  
      
      
      X t
attempt: # 文字列をセット
  str = input()
  flag = 0
  result = "None"
  # 小文字のアルファベットをセット
  for s in str:
      for i in range(97, 97 + 26):
          if flag == 0:
              if chr(i) == s:
                  result = chr(i)
                  flag = 1
          else:
              break
  print(result)
  
problem_description: Statement
  
  We have a sandglass that runs for X seconds. The sand drops from the upper
  bulb at a rate of 1 gram per second. That is, the upper bulb initially
  contains X grams of sand.
  
  How many grams of sand will the upper bulb contains after t seconds?
samples: [{"input": "100 17", "output": "83\n    \n\n17 out of the initial 100 grams of sand will be consumed, resulting in 83\ngrams.\n\n* * *"}, {"input": "48 58", "output": "0\n    \n\nAll 48 grams of sand will be gone, resulting in 0 grams.\n\n* * *"}, {"input": "1000000000 1000000000", "output": "0"}]