import fs from 'fs'

const input = (fs.readFileSync('/dev/stdin', 'utf8') as string).split('\n')
const k = +input[0]
const a = +input[1].split(' ')[0]
const b = +input[1].split(' ')[1]

let result = 'NG'

for (let i = 0; i < 1000; i++) {
  if (a <= i * k && i * k <= b && result === 'NG') {
    result = 'OK'
  }
}

console.log(result)
