Задача 66: Степень двойки (@jinxonik)

GetN.pas

{$APPTYPE CONSOLE}
//{$DEFINE ENTERLEN}
const
  HugeNumber = 1E4000;

var
{$IFNDEF ENTERLEN}
  SourceStr: String;
{$ENDIF}
  Power, SourceLen, CurValLen, TotalLen: Integer;
  CurValue, ControlVal: Extended;

begin
{$IFNDEF ENTERLEN}
  Write('Enter source string: ');
  ReadLn(SourceStr);
  SourceLen := Length(SourceStr);
{$ELSE}
  Write('Enter source string length: ');
  ReadLn(SourceLen);
{$ENDIF}
  if SourceLen <= 0 then WriteLn('String is empty!')
  else
  begin
    Power := 1;
    CurValLen := 1;
    TotalLen := 1;
    CurValue := 2;
    ControlVal := 10;
    while TotalLen < SourceLen do
    begin
      CurValue := CurValue * 2;
      if CurValue >= ControlVal then
      begin
        Inc(CurValLen);
        if ControlVal >= HugeNumber then
        begin
          CurValue := CurValue / HugeNumber;
          ControlVal := ControlVal / HugeNumber;
        end;
        ControlVal := ControlVal * 10;
      end;
      Inc(Power);
      Inc(TotalLen, CurValLen);
    end;
    WriteLn('Power of last number is ', Power, ' (last power value length is ', CurValLen, ' digits)');
  end;
end.