#69 백준 파이썬 [1712] 손익분기점

https://www.acmicpc.net/problem/1712

 

 

 

#Solution

 

f_cost,v_cost,price = map(int, input().split())

num_sales = 0

if v_cost < price:
    num_sales = f_cost // (price - v_cost)   
    print (num_sales+1)
    
else:
    print(-1)