var p,i,j,c:longint;
    n:int64;
    f,g:text;
procedure calcul;
 var i,j:longint;
 begin
  i:=1;
  n:=5;
  while i<p do
   begin
    n:=n+5;
    c:=0;
    j:=n;
    while j mod 5 =0 do
     begin
      c:=c+1;
      j:=j div 5
     end;
    i:=i+c
   end;
  if i>p then
   n:=-1;
  end;
begin
 assign(f,'fact.in');
 reset(f);
 readln(f,p);
 close(f);
 calcul;
 assign(g,'fact.out');
 rewrite(g);
 write(g,n);
 close(g);
end.