#include <iostream>
#include <fstream>

using namespace std ;

ifstream f ( "fact.in" ) ;
ofstream g ( "fact.out" ) ;

int sumaTotala , tintaImpusa ;

int nrMultipli ( int Val )
{
	int rezultat = 0 ;
	while ( Val % 5 == 0 )
	{
		rezultat ++ ;
		Val = Val / 5 ;
	}
	return rezultat ;
}

int main ( ) 
{
	f >> tintaImpusa ;
	int i = 0 ;
	while ( sumaTotala < tintaImpusa )
	{
		i += 5 ;
		sumaTotala += nrMultipli ( i ) ;
	}
	if ( sumaTotala > tintaImpusa )
	{
		cout << -1 << endl ;
		return 0 ;
	}
	cout << i << endl ;
	return 0 ;
}