#include<iostream>
using namespace std;


int main ()
{
	FILE *in=fopen("fact.in","r"),
		 *out=fopen("fact.out","w");
	long long int a,i,r,aux;
	fscanf(in,"%lld",&a);
    aux=5;
    r=aux;
	while (a!=0)
	{
		aux=r;i=0;
		while (aux % 5==0)
		{
			aux=aux/5;
			i++;
		}
		a-=i;
	
		if (a!=0) r+=5;
		if (a<0) {r=-1; goto x;}
	}




x:	fprintf(out,"%lld",r);

	return 0;
	
}