#include<fstream>
using namespace std;
FILE*in;
ofstream out("fact.out");
int f, i, nr0, p, j, x, nr2, nr5;
bool JACK=true;
int main()
{
	in=fopen("fact.in","r");
	fscanf(in,"%d",&p);
	j=1;
	while(JACK)
	{
		f=1;
		nr0=nr2=nr5=0;
		for (i=1; i<=j; i++)
		{
			x=i;
			while (x%2==0)
			{
				x/=2;
				nr2++;
			}
			while (x%5==0)
			{
				x/=5;
				nr5++;
			}
		}
		if (nr2<nr5)
			nr0=nr2;
		else
			nr0=nr5;
		if (nr0==p)
			JACK=false;
		else
			j++;
	}
	out<<j;
	return 0;
}