ORIGINAL Pascal

var m:int64;

function goc(n:int64):int64;
var i:longint;g:int64;
begin
        g:=1;
        for i:=2 to trunc(sqrt(n)) do
        begin
                if n mod i = 0 then g:=g*i;
                while n mod i=0 do
                begin
                        //write(i,' ');
                        n:=n div i;
                end;
        end;
        if n>1 then g:=g*n;
        exit(g);
end;

procedure giai;
begin
        while m>1 do
        begin

                if goc(m)=m then
                begin
                        write(m);
                        exit;
                end;
                dec(m);
        end;

end;

begin
    assign(input, 'goc.inp');reset(input);
    assign(output, 'goc.out');rewrite(output);
    read(m);
    giai;
end.