#include <fstream>

using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");

int main()
{
	int n, m = 0;
	int before = 0, sum = 0, c;
	fin >> n;
	if(n == 0)
		fout << 1;
	while(m <= n)
	{
		before = m;
		m++;
		m *= 5;
	}
	c = before;
	m = before;
	while(m != 0)
	{
		while(c <= n)
		{
			before = c;
			sum += m / 5;
			c += m + 1;
		}
		m = m / 5 - 1;
		c = before + m + 1;
	}
	if(before == n)
		fout << -1;
	else
		fout << (n - sum) * 5;
    return 0;
}