#include<iostream>
#include<fstream>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");

int main()
{
	double p,ok=0,n,,fives=0,pp;
	fin>>p;

	for(n=1;ok==0 && n>0;n++)
	{
		pp=n;
		while(pp%5==0){
			if (pp%5==0) { fives++; pp=pp/5;}
			}

		if(fives>=p)
			ok=n;
	}

	if(fives != p) fout<<-1;
	else fout<<ok;

	fout.close();
	fin.close();

	return 0;
}