output_description: If the wolves will attack the sheep, print `unsafe`; otherwise, print `safe`.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      S W
attempt: A, B, C, D = map(int, input().split())
  ans = "Yes"
  curA = A
  curC = C
  for i in range(max(A, C)):
      curC = curC - B
      if curC <= 0:
          ans = "Yes"
          break
      curA = curA - D
      if curA <= 0:
          ans = "No"
          break
  print(ans)
  
problem_description: Statement
  
  There are S sheep and W wolves.
  
  If the number of wolves is greater than or equal to that of sheep, the wolves
  will attack the sheep.
  
  If the wolves will attack the sheep, print `unsafe`; otherwise, print `safe`.
samples: [{"input": "4 5", "output": "unsafe\n    \n\nThere are four sheep and five wolves. The number of wolves is not less than\nthat of sheep, so they will attack them.\n\n* * *"}, {"input": "100 2", "output": "safe\n    \n\nMany a sheep drive away two wolves.\n\n* * *"}, {"input": "10 10", "output": "unsafe"}]