#include<fstream.h>
#include<math.h>

ifstream fin ("fact.in");
ofstream fout("fact.out");

unsigned long int a, b, p, i, x;
 double n, c;

int main()
{
	fin>>p;
	b= 5*(p+1);
	int gasit = 0;
	do{
		  c=(a+b)/2;
		  n = c/5;
			  
		  i = 1;
		  x = pow(5,i);
			 while(x<=c)
			 {
				 n+=i-1;
				 x = pow(5,++i);
			 }
		  if(p == n)//5
		  {
			gasit = 1;
			fout << c;
		  }
		  else
			  if(n>p)
				  b = c;
			  else
				  a=c;
              
       }while(!gasit && b>=a);
	 if(!gasit)
		fout<<-1;
    
    
 fin.close();
 fout.close();
 return 0;   
}