var i,j,p,x,n,nr:longint;
f,g:text;
begin
assign(f,'fact.in');reset(f);
assign(g,'fact.out');rewrite(g);
read(f,p);
if p=0 then write(g,'1') else begin
 repeat
  n:=1;
  nr:=0;
  inc(x);
  for i:=1 to x do begin
   n:=n*i;
   if n mod 10=0 then begin
                      inc(nr);
                      n:=n div 10;
                      end;
  end;
 until nr=p;
 write(g,x);
 end;    close(g);
end.