#include <iostream>
#include <fstream>
#include <vector>
using namespace std;

int main () {

ifstream in ("fact.in");
ofstream out ("fact.out");

int n, i, count ,temp;

in >> n;
count = 0;
vector <int> list(20, 0);
int number = 1;
for (i = 1;count < n; i++)
{
	if (list.size() <= number)
		list.resize(list.size() * 2, 0);
	if (i % 5 != 0)
	{
		list[i] = 0;
		count++;
	}
	else
	{
		list[i] = list[i/5] + 1;
		count += list[i];
		count ++;
	}
	
	if (count == n)
	{
		out << i * 5;
		break;
	}
	number ++;
}
if (n == 0)
	out << 1;
else
	if (count > n)
		out << -1;
return 0;
}