#include <bits/stdc++.h>
using namespace std;

int main(){
  int K , A , B;
  bool flag=0;
  cin >> K >> A >> B;
  for(int i=1; i<1001 ; i++){
    if(A<=K*i&&K*i<=B)
      flag=1;
  }
  if(flag)
    cout << "OK" << endl;
  else
    cout << "NG" << endl;
}