Rajiv is given a problem in class. 
" Suppose N burnt candles together make a new candle. then how many new candles are created if we start with M candles"

Please refer to similar MCQ Question for clarification.

SAMPLE INPUT
121

SAMPLE OUTPUT
30
n = int(raw_input())
ans = n / 5
r = n % 5 + ans
while r  >= 5:
	ans += r / 5
	r = r % 5 + r / 5
print ans