#include <fstream>

using namespace std;
#define ll long long

ll zero(ll c)
{ll p;
  for(p=0;c;p+=c/5 ,c/=5);
	return p;
}

ll  p , a , b , c , fn , i ;
bool ok;

int main()
{
	ifstream fin("fact.in");
	ofstream fout("fact.out");
	fin>>p;
	a=4 * p, b=5 * p , c=a + (b-a)/2 , c=c-c%5;  
	while(a<=c && c<=b && a<=b && !ok)  
	{  
	fn = zero(c); 
    if(fn==p)  ok = true , i = c;  
    else 
	if(fn<p)  
    a = c + 1;  
    else  
    b=c-1;  
    c=a + (b-a)/2;  
    c-=c%5;  
   }  
	if(!p) fout<<1;
	else
	if(!ok) fout<<-1;
	else
	 fout<<i-i%5;
	return 0;
}