HARDCORE_LABA_02.pas

var
  input, output: string;
  endpoint, size: integer;
  I, J, K, L: integer;
  dirright: boolean;
  arr: array of array of char;
begin
  try
    readln(input);
    endpoint := pos('.', input);
    if (endpoint < 1) or (length(input) = 0) then
      writeln('Входная строка имела неверный формат.')
    else
      begin
        input := copy(input, 1, endpoint - 1);
        size := ceil(sqrt(length(input)));
        setlength(arr, size, size);
        for I := 0 to size - 1 do
            for J := 0 to size - 1 do
              begin
                if (I * size) + (J + 1) <= endpoint - 1 then
                  arr[I, J] := input[(I * size) + (J + 1)]
                else
                  arr[I, J] := '#';
              end;

        K := 0;
        L := 0;
        I := 0;
        J := 0;
        while (k < size) and (l < size) do
          begin

            output := output + arr[j, i];
            if not dirright then
            begin
              j := j + 1;
              if j > size - 1 then
              begin
                k := k + 1;
                dirright := true;
                i := k;
                j := l;
              end;
            end
              else
                begin
                  i := i + 1;
                  if i > size - 1 then
                    begin
                      l := l + 1;
                      dirright := false;
                      i := k;
                      j := l;
                    end;
            end
          end;

        writeln(output);
        read;
      end;

  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;