#include <fstream.h>
#include <iostream.h>
#include <math.h>
int main()
{
	long long int p,crt,zerouri=0,i,k;
	fstream f,g;
	f.open("fact.in",ios::in);
	f>>p;
	f.close();
	g.open("fact.out",ios::out);
	crt=0;
	while(zerouri<p)
	{	zerouri=0;
		k=1;
		while(crt>pow(5,k))
		{
			zerouri+=(crt/(pow(5,k)));
			k++;
		}
	crt+=5;


	}
	if(zerouri==p)
	g<<crt-5;
	else
	g<<-1;

	g.close();
return 0;}