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


 
int main ()
{  
 
ifstream f("fact.in");
ofstream g("fact.out");
long long x,p,m,s,d,ok=0,nr;

f>>p;

if(p==0) g<<1;
else

	{
		s=0;
		d=p*5;
		
		while(s<=d)
		{
			m=(s+d)/2;
			nr=m;
			x=0;
			
			while(nr)
			{
				x=x+nr/5;
				nr/=5;
			}
			
			if(x==p)
				ok=1;
			
		 	if(x>=p)
				d=m-1;
			else
				s=m+1;
		}
	
		if(ok==1)
		{
			if(m%5!=0)
				while(m%5!=0)
					m++;
			g<<m;
		}
		 else
	 	g<<-1;
	}
 
return 0;
}