#include <iostream>
#include <fstream>

using namespace std;

int main () {

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

int n, i, count;

in >> n;
count = 0;

for (i = 1;count < n; i++)
{
	if (i % 5 != 0)
		count++;
	else
		count += i/5 + 1;
	
	if (count == n)
	{
		out << i * 5;
		break;
	}

}
if (n == 0)
	out << 1;
else
	if (count > n)
		out << -1;
return 0;
}