def intervalAdd(self, a, b, val):
        """Variant, adds val to t[a], to t[a + 1] ... and to t[b]

        :param int a b: with 1 <= a <= b
        """
        self.add(a,     +val)
        self.add(b + 1, -val)
Variant, adds val to t[a], to t[a + 1] ... and to t[b]

        :param int a b: with 1 <= a <= b