Решение СЛАУ методом Гаусса-Зейделя - VB

Dim a(1 To 4, 1 To 4) As Double
Dim b(1 To 4) As Double
Dim x(1 To 4) As Double
Private Sub Command1_Click()
a(1, 1) = -8
a(1, 2) = -1
a(1, 3) = -4
a(1, 4) = 10
b(1) = 4
 
a(2, 1) = 8
a(2, 2) = 8
a(2, 3) = 2
a(2, 4) = -4
b(2) = 7
 
a(3, 1) = 6
a(3, 2) = 4
a(3, 3) = 1
a(3, 4) = -4
b(3) = -1
 
a(4, 1) = 10
a(4, 2) = 27
a(4, 3) = -4
a(4, 4) = -5
b(4) = 6
e = 0.0001
n = 4
Do
    M = 0
    For i = 1 To n
            s = 0
        For J = 1 To n
          If i <> J Then s = s + a(i, J) * x(J)
        Next
        v = x(i)
        x(i) = (b(i) - s) / a(i, i)
        M = Abs(x(i)) - Abs(v)
    Next
    'Next
  Loop Until M < e
 
' вывод результата
For i = 1 To 4
Debug.Print x(i)
Next
Debug.Print 6 * x(1) + 4 * x(2) + 1 * x(3) - 4 * x(4) 'должно выводить -1
End Sub