Imports System
Public Class Program
Private Shared Function getEquilibriumIndex(ByVal arr As Integer()) As Integer
Dim sum_arr As Integer = 0
Dim left_part_sum As Integer = 0
Dim size As Integer = arr.Length
For i As Integer = 0 To size - 1
sum_arr += arr(i)
Next
For i As Integer = 0 To size - 1
sum_arr -= arr(i)
If left_part_sum = sum_arr Then
Return i
End If
left_part_sum += arr(i)
Next
Return -1
End Function
Public Shared Sub Main(ByVal args As String())
Dim arr As Integer() = New Integer() {-9, 2, 5, 8, -7, 4, 1}
Console.Write("equilibrium index = " & getEquilibriumIndex(arr))
End Sub
End Class
' run:
'
' equilibrium index = 3
'
