#include <fstream.h>

unsigned long p,q,n,i,k;


int main()
{
	ifstream be("fact.in");
	ofstream ki("fact.out");
	unsigned long v[100];
	memset((void*)v, 0, 25*sizeof(unsigned long));

	be >> p;

	while(q<p)
	{
		v[0]++; q++; n++;
		k=0;
		while(v[k]==5) {q++; v[k++]=0; v[k]++;}
	}

	if (q==p)
	{
		if (p==0) ki << 1;
		else ki << n * 5;
	}
	else
		ki << -1;

	//be.close();
	//ki.close();
	return 0;
}