let k = Int(readLine()!)!
let i = readLine()!
    .split(separator: " ")
    .map { Int($0)! }
let (a, b) = (i[0], i[1])
let x = (a...b).contains { $0.isMultiple(of: k) }
let y = (a == b) && (a == k)
print(x || y ? "OK" : "NG")