#include <iostream>

int main()
{
  int k, a, b;
  std::cin >> k >> a >> b;
  
  bool isOK = false;
  for(int i = a; i <= b; ++i)
  {
    if(i % k == 0)
    {
      isOK = true;
      break;
    }
  }
  
  std::cout << (isOK? "OK" : "NG") << std::endl;
  return 0;
}