#include <bits/stdc++.h>

using namespace std;

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