#include <bits/stdc++.h>
using namespace std;
#define rep(i, a) for(int i=0; i<(a); i++)
typedef long long ll;

int main()
{
  ll k;
  cin >> k;
  ll a;
  cin >> a;
  ll b;
  cin >> b;
  for (int i=a; i<=b; i++) {
    if (i%k == 0) {
      cout << "OK" << endl;
      return 0;
    }
  }
  cout << "NG" << endl;

  return 0;
}
