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

int main() {
  int n, k, a, b;
  cin >> k;
  cin >> a >> b;
  if(a%k==0||b%k==0) cout << "OK" << endl;
  if(a%k!=0&&b%k!=0){
    n=b-a;
  if(n<=k) cout << "OK" << endl;
  }
  else cout << "NG" << endl;
}
