#include<iostream>
using namespace std;
int main()
{
  int k,a,b;
  cin>>k>>a>>b;
  int min;
  min=a/k;
  min++;
  if(a%k==0 || b%k==0 || min*k<=b)
  {
        cout<<"OK\n";
  }
  else
  {
    cout<<"NG\n";
  }
  return 0;
  
  
}