#include <algorithm>
#include <array>
#include <cmath>
#include <deque>
#include <iostream>
#include <set>
#include <string>

using namespace std;

int main() {
  int k, a, b;

  cin >> k >> a >> b;

  bool flag = false;

  for (int i = a; i <= b; i++) {
    if (i % k == 0) {
      cout << "OK" << endl;
      flag = true;
      break;
    }
  }

  if (!flag) {
    cout << "NG" << endl;
  }

  return 0;
}