#!/usr/bin/env python

def nr_zerouri(n):
    nr = 0
    while(n):
        if n % 10 != 0:
            break
        nr += 1
        n //= 10
    return nr

def factorial(n):
    if n == 0 or n == 1:
        return 1
    result = 1
    for x in range(2, n+1):
        result *= x
    return result

file_in = open("fact.in", "r")
file_out = open("fact.out", "w")

p = int(file_in.readline())
if p == 0:
    file_out.write("1")
    file_in.close()
    file_out.close()
    exit()

INCREMENT = 5
x = 5
while True:
    fact = factorial(x)
    nr = nr_zerouri(fact)
    if nr > p:
        file_out.write("-1")
        break
    if nr == p:
        file_out.write(str(x))
        break
    x += INCREMENT

file_in.close()
file_out.close()