PRIME1032 PAS

const   fin = 'prime1032.inp';
    fon = 'prime1032.out';
var
   p:array[1..2000000] of byte;
   a:array[1..1000000] of longint;
   m,n,b,i,j,max,d:longint;

function ktnt(n:int64):boolean;
var i:longint;
begin
    if n<2 then exit(false);
    if (n=2) or (n=3) then exit(true);
    for i:=2 to trunc(sqrt(n)) do
           if n mod i = 0 then exit(false);
    exit(true);
end;


procedure sang;
var i,j:longint;
begin
    p[1]:=1;
    for i:=2 to trunc(sqrt(b)) do
        if p[i]=0 then
        begin
            j:=i*i;
            while j<=b do
            begin
                p[j]:=1;
                j:=j+i;
            end;
        end;
end;
procedure tao_mang_nt;
var i:longint;
begin
    d:=0;
    for i:=1 to b do
        if p[i]=0 then
        begin
            inc(d);
            a[d]:=i;
        end;
end;
begin
    assign(input,fin);reset(input);
    assign(output,fon);rewrite(output);
    read(n);
    b:=trunc(sqrt(n));
    sang;
    tao_mang_nt;
    max:=0;
    for i:=1 to d do
    begin
        for j:=n div a[i] downto a[i+1] do
            if ktnt(j) = true then
            begin
                if a[i]*j>max then max:=a[i]*j;
                break;
            end;
    end;
    write(max);
    close(input);close(output);
end.