class summ:
    def __init__(self):
        self.t = float(0)
        self.c = float(0)
    def push(self, x):
        y = x - self.c
        s = (self.t + y)
        self.c = (s - self.t) - y
        self.t = s
    def __float__(self):
        return self.t + self.c

def disp2(seq):
        sumx = summ()
        res = summ()

        n = 0

        #formula for dispersion when average is changing by delta:
        #sum(x[i]^2) - 2*sum(x[i])*aver - 2*sum(x[i])*delta +
        #2*aver*delta * (N - 1) + aver^2 * (N - 1) + delta^2 * (N - 1)

        for x in seq:
            n += 1
            old_sum = float(sumx)
            old_aver = old_sum
            if (n > 1): old_aver /= (n - 1)

            sumx.push(x)

            cur_aver = float(sumx) / n

            delta = cur_aver - old_aver

            res.push(-2 * old_sum * delta)
            res.push(2 * old_aver * delta * (n - 1))
            res.push(delta ** 2 * (n - 1))
            #changed old sums

            res.push((cur_aver - x) ** 2)
            #added current

        return float(res) / n