var f,g:text;
    n,p,c2,c5,copie:longint;
begin
 assign(f,'fact.in');reset(f);
 assign(g,'fact.out');rewrite(g);
 readln(f,p);
 if p>=0 then begin
                 n:=0;
                 c2:=0;
                 c5:=0;
                 repeat
                   n:=n+1;
                   copie:=n;
                   while (copie mod 2=0) and (c2<p) do begin
                       c2:=c2+1;
                       copie:=copie div 2;
                   end;
                   while (copie mod 5=0) and (c5<p) do begin
                       c5:=c5+1;
                       copie:=copie div 5;
                   end;
                 until ((c2=p)and(c5>=c2)) or ((c5=p)and(c2>=c5));
                 if n>0 then write(g,n)
                        else write(g,'-1');
               end
          else write(g,'-1');
 close(f);
 close(g);
end.