var f,g:text;
     p,n,s,a,b,x :longint;
begin
assign(f,'fact.in');reset(f);
assign(g,'fact.out');rewrite(g);
read(f,p);
while s<p do
  begin
  n:=n+1;
  x:=n;
  while x mod 5 = 0 do
    begin
    a:=a+1;
    x:=x div 5;
    end;
  while x mod 2 = 0 do
    begin
    b:=b+1;
    x:=x div 2;
    end;
  if a > b then
    s:=b
  else
    s:=a;
  end;
write(g,n);
close(g);
end.