function Node(idx) {
	  this.idx = idx;
	  this.starts = new SortedList({
	    compare: function compare(a, b) {
	      if (a == null) return -1;
	      if (b == null) return 1;
	      var c = a.start - b.start;
	      return c > 0 ? 1 : c == 0 ? 0 : -1;
	    }
	  });

	  this.ends = new SortedList({
	    compare: function compare(a, b) {
	      if (a == null) return -1;
	      if (b == null) return 1;
	      var c = a.end - b.end;
	      return c < 0 ? 1 : c == 0 ? 0 : -1;
	    }
	  });
	}
Node : prototype of each node in a interval tree