#include <fstream.h>
ifstream f("fact.in");
ofstream g("fact.out");
int main()
{
int n,i=0,nr2=0,nr5=0,nr0=0;
f>>n;
while (nr0<n)
	{
	i++;
	int aux=i;
	while (aux%2==0)
		{
		nr2++;
		aux/=2;
		}
	while (aux%5==0)
		{
		nr5++;
		aux/=5;
		}
	if (nr2>=1&&nr5>=1)
		{
		int dif;
		if (nr2<nr5) dif=nr2;
		else dif=nr5;
		nr0+=dif;
		nr2-=dif;
		nr5-=dif;
		}
	}
if (n==0)
	i++;
g<<i;
return 0;

}