Imports System.IO
Module Module1

    Sub Main()
        Dim fs As New FileStream("DATA1.txt", FileMode.Open, FileAccess.Read)
        Dim fso As New FileStream("OUT1.txt", FileMode.Create, FileAccess.Write)
        Dim text As New StreamReader(fs)
        Dim texto As New StreamWriter(fso)

        Dim line As String
        Dim length(2) As Double
        Dim x, y, c, a, b As Decimal
        Dim angle, values As Double
        Dim num(3) As String
        line = text.ReadLine
        num = line.Split(" ")
        length(0) = Math.Sqrt((Val(num(0)) * Val(num(0))) + (Val(num(1)) * Val(num(1))))
        length(1) = Math.Sqrt((Val(num(2)) * Val(num(2))) + (Val(num(3)) * Val(num(3))))
        x = Val(num(0)) - Val(num(2))
        y = Val(num(1)) - Val(num(3))
        length(2) = Math.Sqrt((x * x) + (y * y))
        c = length(0)
        a = length(2)
        b = length(1)
        values = Math.Acos(((c * c) + (b * b) - (a * a)) / (2 * b * c))
        angle = (values * 180) / Math.PI
        If num(1) = 0 Then
            angle = 360 - angle
        End If
        texto.WriteLine(FormatNumber(angle, 1) & vbCr)

        texto.Close()
        text.Close()
        fs.Close()
        fso.Close()
    End Sub

End Module