#include<fstream.h>
#include<math.h>
int main()
{long i,s=0,p;
 ifstream f("fact.in");
 ofstream g("fact.out");
 f>>p;
 if(p%5==0&&p%2==1)g<<"-1";
 else
	{for(i=1;i<=p;i++)
		if(!(i%5==0&&i%2==1))
			s=s+5;
	 g<<s;
	 }
 g.close();
 return 0;}