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


const int MAX_SIZE=33554430;

int v[MAX_SIZE];
int k[MAX_SIZE];
int n;
ofstream g("fact.out");



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()
{

	int x=0;
	do
	{
		x+=5;
		k[x]=k[x/5]+1;
		v[x]=v[x-5]+k[x/5]+1;
	}while(v[x]<=n);

	int i;
	/*for(i=5; v[i]<=n; i+=5)
		cout<<i<<" "<<v[i]<<endl;*/
	//cout<<v[x-5];
	if(v[x-5]==n)
		g<<x-5;
	else
		g<<-1;
}

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