function calculate() {
  var fileList = DocsList.getFiles();
  var count = fileList.length;
  var file;
  var i;
  var theSheet = SpreadsheetApp.getActiveSheet();

  theSheet.clear();
  theSheet.getRange(1, 1).setValue("File Name");
  theSheet.getRange(1, 2).setValue("File Location(s)");
  theSheet.getRange(1, 3).setValue("File Size");
  for (i=0; i<count; i++)
  {
    file = fileList[i];
    theSheet.getRange(i+2, 1).setValue(file.getName());
    theSheet.getRange(i+2, 3).setValue(file.getSize());

    var folders = file.getParents();
    var folderNames = "";
    var fIdx;
    for (fIdx in folders)
    {
      folderNames = folders[fIdx].getName() + "; " + folderNames;
    }
    theSheet.getRange(i+2, 2).setValue(folderNames);
  }

  theSheet.sort(3, false);
  theSheet.getRange(2, 3, count, 1).setNumberFormat("#,##0")
}