function main(arg) {
  var K = parseInt(arg[0]);
  var [A,B] = arg[1].split(" ")
  var result = "NG";
  for(var i = parseInt(A); i <=　parseInt(B); i ++) {
  	if(i % K == 0) {
      result = "OK"
    }
  }
  console.log(result)
}

main(require("fs").readFileSync("/dev/stdin", "utf8").trim().split("\n"));
