#include<iostream>
#include<fstream>
using namespace std;
int main()
{long long p,i=0,nr=0,nr2=0,nr5=0,min,cat,rest;
ifstream f("fact.in");
ofstream g("fact.out");
f>>p;
if(p==0)
	g<<1;
else
{
    while(nr<p)
	{i=i+5;cat=i/5;
	while(cat>0)
	{nr5=nr5+1;cat=cat/5;}
	cat=i/2;rest=i%2;
	if(rest==0)
		nr2=nr2+1;
	while(cat>0)
	{nr2=nr2+cat;cat=cat/2;}
	if(nr2>nr5)
		min=nr5;
	else
		min=nr2;
	if(min>=p)
		nr=min;}
	
	
}
if(nr==p)
	g<<i;
else
	g<<-1;
f.close();
g.close();
return 0;
}