#include<iostream>
#include<fstream>
#include<limits.h>

#define fin "fact.in"
#define fout "fact.out"

int find_nr_0(int n)
{
	
	int aux = 5;
	int nr = 0;
	while (n >=aux)
	{
		nr += n / aux;
		aux *= 5;
	}
	return nr;
}
int find_number(int n)
{
	if (n == 0)
	{
		return 0;
	}
	int left = 1, right = 2000000000;
	while (left<right)
	{
		int m = (left + right) / 2;
		int aux = find_nr_0(m);
		if (aux == n)
		{
			return m-m%5;
		}
		else
		{
			if ( aux < n)
			{
				left = m + 1;
			}
			else
			{
				right = m - 1;
			}
		}
	}
	return -1;
}
int main()
{
	std::fstream in;
	int n;
	in.open(fin, std::ios::in);
	in >> n;
	in.close();

	std::fstream out;
	out.open(fout,std::ios::out);
	int res= find_number(n);
	out << res;
	out.close();
	return 0;
}