' aのn乗をmで割った余りを返す
Function LargeMod(ByVal a As Long, ByVal n As Long, ByVal m As Long)
    
    Dim result As Long
    result = a Mod m
    
    If n >= 2 Then
        For i = 2 To n
            result = (result * a) Mod m
        Next i
    End If

    LargeMod = result
    
End Function