def inner_solve(u, data):
        d = data[0, :]
        u1 = data[1, 2:]
        u2 = data[1, 4:]
        n = d.shape[0]
        u[n-1] = u[n-1]/d[n-1]
        u[n-2] = u[n-2]/d[n-2]
        u[n-3] = (u[n-3]-u1[n-3]*u[n-1])/d[n-3]
        u[n-4] = (u[n-4]-u1[n-4]*u[n-2])/d[n-4]
        for i in range(n - 5, -1, -1):
            u[i] = (u[i] - u1[i]*u[i+2] - u2[i]*u[i+4])/d[i]