#include <stdio.h>

int p;

void cautare()
{
	int puteri = 0,clim,lim;
	for (lim = 1; puteri < p; ++lim)
	{
		clim = lim;
		while (clim % 5 == 0)
		{
			++puteri;
			clim /= 5;
		}
	}
	printf ("%d",lim-1);
}

int main()
{
	freopen ("fact.in","r",stdin);
	freopen ("fact.out","w",stdout);
	scanf ("%d",&p);
	if (p == 0)
		printf ("1");
	else
		cautare();
	return 0;
}