Count the Hidden Sequences

class Solution:
    def numberOfArrays(self, differences: List[int], lower: int, upper: int) -> int:
        mx, mn = float("-inf"), float("+inf")
        ps = 0
        for i in differences:
            ps += i
            mx = max(ps, mx)
            mn = min(ps, mn)
        r1 = upper-lower+1
        if mx == mn:
            r2 = abs(mx)
        else:
            r2 = mx - mn
        return max(r1-r2, 0)