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

ofstream g("fact.out");

const int MAX=30000;

int n;
map<int,int> v;


inline void citire();
inline void add_data();
int main()
{
	citire();

	if(n==0)
	{
		g<<1;
		g.close();
		return 0;
	}

	add_data();

	g.close();
	return 0;
}


inline void add_data()
{
	v[1]=1;

	int x=2;
	do
	{
		if(x%5!=0)
			v[x]=v[x-1]+1;
		else
			v[x]=v[x-1]+v[x/5]+1;

		x++;
	}while(v[x-1]<=n);

	/*map<int,int>::iterator  i;
	for(i=v.begin(); i!=v.end(); i++)
	{
		cout<<i->second<<" ";
	}
	cout<<endl<<x-2;*/

	if(v[x-2]==n)
		g<<((x-2)*5);
	else
		g<<-1;
}

inline void citire()
{
	std::ifstream f("fact.in");
	f>>n;
	f.close();
}