#include <fstream.h>
#include <iostream.h>
#include <math.h>
int main()
{
	long long int p,crt,zerouri=0,i,k;
	long long int x[50];
	x[0]=1;
	for(i=1;i<=49;i++)
		x[i]=x[i-1]*5;
	fstream f,g;
	f.open("fact.in",ios::in);
	f>>p;
	f.close();
	g.open("fact.out",ios::out);
	crt=5;   int ok;
	while(zerouri<p)
	{       ok=0;
		for(i=1;i<=49;i++)
			if(crt==x[i])
			{	zerouri+=i; ok=1;
				break;
			}
		if(!ok)
		{
		k=crt;
		while(k%5==0)
		{	zerouri++;
			k/=5;
		}
		}
		crt+=5;
	}
	if(zerouri==p)
		g<<crt-5;
	else
		g<<-1;
	g.close();
	return 0;
}