let aa = Int(readLine()!)!
let arr=readLine()!.split{$0==" "}.map{Int(String($0))!}
var a=arr[0]
var b=arr[1]
var i = 0
while a <= b {
    if a%aa == 0 {
        print("OK")
        i = 1
        break
    }
    a+=1
}
if i == 0 {
    print("NG")
}