const main = input => {
  let lines = input.split('\n')
  let k = Number(lines[0])
  let a = lines[1].split(' ').map(e=>Number(e))
  
  for(let i = a[0]; i <= a[1]; i++) {
    if(i%k == 0) return "OK"
  }
  return "NG"
}

console.log(main(require("fs").readFileSync("/dev/stdin", "utf8")))