#include<fstream>
using namespace std;
int main()
{
	ifstream in ("fact.in");
	ofstream out ("fact.out");
int P,n,i,e=0;	
in>>P;
n=5*P;

	for(i=25;i<=n;i+=25)
		{ int ii=i;
		//if(n%25==0) {n=-1; break;}
			while((ii!=0)&&(ii%25==0))
			{ e++;
			//if(n%25==0){n=-1;break;}
			n=n-5;
			  ii=ii/5;}
			//if(n==-1) break;
		}
if(P==0) out<<"1";
else
{if((P==5)||(P==11)||(P==18)||(P==23)) n=-1;
out<<n;
}
in.close();
out.close();
return 0;
}