Module C
    Sub Main()
        Dim input As String = Console.ReadLine()
        Dim arr() As String = Split(input, " ")
        Dim a, b As Integer
        a = arr(0) : b = arr(1)
        Dim wk As Integer = -1
        For i As Integer = 1 To 1000
            If Math.Floor(i * 0.08) = a AndAlso Math.Floor(i * 0.1) = b Then
                wk = i
                Exit For
            End If
        Next
        Console.WriteLine(wk)
    End Sub
End Module