let n = Int(readLine()!)!
    var r: Int = 0
    
    var num = readLine()!.split(separator: " ").compactMap{Int($0)}
    
    var ns = num[0]
    
    for _ in ns ... num[1] {
      
      if ns % n == 0 {
        print("OK")
        r += 1
        break
      }
      ns += 1
    }
    if r == 0 {
    print("NG")
    }