import Foundation

let input: String = readLine()!
let k = Int(input)!

let input_line: String = readLine()!
let split: [String] = input_line.components(separatedBy: " ")

let a = Int(split[0])!
let b = Int(split[1])!

var ans = "NG"

var j = 0
var i = 1
repeat {
    i += 1
    j = k * i
    if j >= a && j <= b {
        ans = "OK"
        break
    }
} while ( b > j )

print(ans)