text: # Title: 손익분기점
  # Link: https://www.acmicpc.net/problem/1712
  
  import sys
  import math
  
  sys.setrecursionlimit(10 ** 6)
  
  
  read_list_int = lambda: list(map(int, sys.stdin.readline().strip().split(' ')))
  
  
  def solution(a: int, b: int, c: int):
      if c-b <= 0:
          return -1
      if a/(c-b) == a//(c-b):
          return (a//(c-b)) + 1
      return math.ceil(a/(c-b))
  
  
  def main():
      a, b, c = read_list_int()
      print(solution(a, b, c))
  
  
  if __name__ == '__main__':
      main()