text: def resolve():
      '''
      code here
      '''
      A, B, C, D = [int(item) for item in input().split()]
  
      turn = 0
      while A > 0 and C > 0:
          turn += 1
          # print(turn, A, C)
  
          if turn % 2 == 1:
              C -= B
          else:
              A -= D
          
          # print(A, C)
      
      
      if A <= 0:
          print('No')
      else:
          print('Yes')
  
  if __name__ == "__main__":
      resolve()
  