function Main(input) {
  let temp = input.split('\n');
  let temp2 = temp[1].split(' ');
  const K = parseInt(temp[0]);
  const A = parseInt(temp2[0])
  const B = parseInt(temp2[1])

  let ans = 'NG';
  if (!(A % K) || Math.floor(A / K) * K + K <= B){
    ans = 'OK'
  }

  // OK or NG
  console.log(ans)
}

// Main('7\n500 600')

// Don't edit this line!
Main(require("fs").readFileSync("/dev/stdin", "utf8"));