Option Explicit On

Module Module1

    Sub Main()

        Dim K As Integer = Console.ReadLine()
        Dim tmp As String() = Split(Console.ReadLine(), " ")
        Dim A As Integer = CInt(tmp(0))
        Dim B As Integer = CInt(tmp(1))

        Dim p1 = A Mod K
        If p1 = 0 Or (A + (K - p1)) <= B Then
            Console.WriteLine("OK")
        Else
            Console.WriteLine("NG")
        End If

    End Sub

End Module
