function mainB() {
  var n = 8;
  var ui = SpreadsheetApp.getUi()
  var result = ui.prompt('Okno', 'Podaj tresc maila', ui.ButtonSet.OK_CANCEL);
  var message = result.getResponseText();
  var button = result.getSelectedButton();

  if (button == ui.Button.OK)
  {
    var sheet = SpreadsheetApp.getActiveSheet();
    var dataRange = sheet.getRange(2, 2, n, 1);
    var data = dataRange.getValues();
    var subject = "Tresc Maila";

    for (i in data)
    {
      var row = data[i];
      var emailAddress = row[0];
      GmailApp.sendEmail(emailAddress, subject, message);
    }
  }else
  {
   ui.alert('Anulowano');
  }

}