program zysfj;
var n,i,j,k:longint;
begin
assign(input,'prime.in');reset(input);
assign(output,'prime.out');rewrite(output);
 read(n);
 for i:= n downto 1 do
  if(n mod i=0)then
   begin
    j:=0;
    for k:=2 to (n div i)-1 do
     if((n div i) mod k=0)then
      begin
       j:=10;
       break;
      end;
    for k:=2 to i-1 do
     if(i mod k=0)then
      begin
       j:=10;
       break;
      end;
    if(j<>10)then
     begin
     writeln(i);
     break;
     end;
   end;
close(input);
close(output);
end.