Задача о системах счисления - Pascal

program test;
 
var
  x: uint64;
  Base: uint64;
  Dividend, Remainder, LastDigit: uint64;
  Res: boolean;
  XisPrime: boolean;
begin
  readln(X);
  XisPrime := True;
  Base := 2;
  while Base < X do
  begin
    Res := True;
    Dividend := X;
    LastDigit := X mod Base;
    XisPrime := XisPrime and (LastDigit <> 0);
    repeat
      Remainder := Dividend mod Base;
      Dividend := Dividend div Base;
      Res := Res and (Remainder = LastDigit);
    until Dividend = 0;
    if Res then
      break;
    Inc(Base);
    if (Base > round(sqrt(X))) and XisPrime then
      Base := X - 1;
  end;
  writeln(Base);
end.