import Foundation

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

func main(){
    
    let k = Int(readLine()!)!
    let ab = readInts()
    
    for i in 1...1000{
        if k*i >= ab[0] && k*i <= ab[1]{
            print("OK")
            return
        }
    }
    print("NG")
    
    
    
}
main()
