#include<bits/stdc++.h>

#define rep(i, n) for(int i = 0; i < (n); ++i)

using namespace std;

using ll = long long;
using P = pair<int , int>;
  
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);

  int k, a, b; cin >> k >> a >> b;

  for(int i = 1; i*k <= b; ++i) {
    if(i*k >= a) {
      if(i*k <= b) {
	cout << "OK";
	return 0;
      }
    }
  }
  cout << "NG";
}
