#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<ll, ll> P;

int main(){
  int K, A ,B;
  cin >> K >> A >> B;

  for (int i = A; i <= B; i++) {
      if (i % K == 0) {
          cout << "OK" << endl;
          return 0;
      }
  }
  cout << "NG" << endl;
  return 0;
}
