import Foundation

private func readInt() -> [Int]{
    return readLine()!.split(separator: " ").map{Int($0)!}
}

func mainA() {
    let K = Int(readLine()!)!
    let line = readInt()
    let A = line[0]
    let B = line[1]
    
    for i in A...B {
        if i % K == 0 {
            print("OK")
            return
        }
    }
    
    print("NG")
}

mainA()
