code: function (items) {
                  var
                      idx;
                  idx = items.length;
                  while (idx--) {
                      if (0 !== items[idx].min()) {
                          ++idx;
                          break;
                      }
                  }
                  return idx;
              }
docs: Return the position from which all items can be optional
  
  @param {PatterItem[]} items
  @return {Number}
  @private