#include<iostream>
#include<fstream>
using namespace std;

long nrDeCinci(long x)
{
	if(x%5!=0)
		return 0;
	if(x<5)
		return 0;
	return 1+nrDeCinci(x/5);
}
long getn(long x,long nrz)
{
	nrz-=(1+nrDeCinci(x));
	if(nrz == 0)
		return 5*x;
	if(nrz < 0)
		return -1;		
	return getn(x+1,nrz);
	
}
int main()
{
	long p,n;
	
	ifstream f("fact.in");
	f>>p;
	f.close();
	
	n=(p==0)?1:getn(1,p);
	
	ofstream g("fact.out");
	g<<n<<"\n";
	g.close();
	return 0;
}