#include <fstream>

using namespace std;

int main()
{
	ifstream IN ("fact.in");
	ofstream OUT ("fact.out");

	int p; IN >> p;
	int noo5 = 0, index = 0, check;

	if (p == 0)
	{
		OUT << "1\n";
		return 0;
	}

	else
	{
		while (noo5 < p)
		{
			index += 5;
			check = index;
			while (check % 5 == 0)
			{
				check /= 5;
				/*if (check > 0)
					noo5++;*/

				noo5++;
			}
		}
	}

	OUT << index << "\n";

	return 0;
}