#include <iostream>
#include <string>
using namespace std;
typedef long long ll;

int K, A, B;

int main() {
  cin >> K;
  cin >> A >> B;
  
  string res = "NG";
  for (int i = A; i <= B; i++) {
    if (i % K == 0) res = "OK"; 
  }
  
  cout << res << endl;
}