def inner_solve(u, data):
        d = data[0, :]
        u1 = data[1, 2:]
        n = d.shape[0]
        u[n-1] = u[n-1]/d[n-1]
        u[n-2] = u[n-2]/d[n-2]
        for i in range(n - 3, -1, -1):
            u[i] = (u[i] - u1[i]*u[i+2])/d[i]