#include <iostream>
#include <fstream>

using namespace std;

int main()
{
	fstream fin("fact.in", ios::in);
	fstream fout("fact.out", ios::out);
	int p, k = 0, x = 1, N;
	cout << "P: ";
	fin >> p;

	if (p < 1)
	{
		fout << "-1";
	}
	else
	{
		while (k < p)
		{
			N = 5 * x;
			while (N % 5 == 0)
			{
				k++;
				N /= 5;
			}
			x++;
		}
		fout << 5*x - 5;
	}
}