#include<fstream>
#include<climits>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int main()
{
	int m,p,k,i=1,j=LONG_MAX,x,ok=0;
	fin>>p;
	if(p==0)fout<<"1";
	while(i<=j&&ok==0){
	m=(i+j)/2;
	x=5;
	k=0;
	while(x<=m){k=k+m/x;
	x=x*5;}
	if(k==p)ok=1;
	else if(k>p)j=m-1;
	else i=m+1;}
	if(ok==0)fout<<"-1";
	else {while(m%5!=0)m--;
	fout<<m;}
	fin.close();
	fin.close();
	return 0;
}