For an integer n not less than 0, let us define f(n) as follows:    * f(n) = 1 (if n < 2)   * f(n) = n f(n-2) (if n \geq 2)  Given is an integer N. Find the number of trailing zeros in the decimal notation of f(N).
n = int(input())
#a,b = map(int,input().split())
N = n
cnt = 0
num = 0
while N:
    cnt += n//5**num
    num += 1
    N = N//5
print(cnt)
n = int(input())
if n%2 ==1:
    print(0)
    exit()
cnt = 0
i = 1

if n%2 == 0:
    while n//(2*(5**i)) > 0:
        cnt += n//(2*(5**i))
        i +=1
print(cnt)