#include<fstream.h>

int nrzn(int n);

void main()
{	int p,n,st,dr,c,nrz;
	ifstream f("fact.in");
	ofstream g("fact.out");
	f>>p;
	st=1;dr=1000000000;n=1;
	if(p>0)
	   while(n)
		{c=(st+dr)/2;
		 nrz=nrzn(c);
		 if(nrz==p&&st==dr) {n=st;break;}
		 if(dr<st) {n=-1;break;}
		 if(p>nrz) st=c+1;
			else	  dr=c-1;
		}
	else g<<n;
	g<<n;
	f.close();
	g.close();
}

int nrzn(int n)
{ 	int nrz=0;
	while(n)
	     {nrz+=n/5;n/=5;}
	return nrz;
}