#include <fstream.h>
using namespace std;
int main()
{ long long k,ci,m,p,nr5,st,dr;
ifstream f1("fact.in");
ofstream f2("fact.out");
cin>>k;
st=1;
dr=2000000000;
if (k==0) f2<<"1";
else
	while (st<=dr)
		{
		m=(st+dr)/2;
		nr5=0;p=5;da
		while(m/p!=0)
			{
			nr5=nr5+(m/p);
			p=p*5;
			}
		if(nr5==k) 
			{ 
			while(m%5!=0) m--;
			cout<<m;  
			return 0;
			}
		else if(nr5>k) dr=m-1;
		else st=m+1;
		}
f2<<"-1";
return 0;
}