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

int main(){
  int K,A,B;
  cin >> K>>A>>B;
  int ans=0;
  
  for(int i=A;i<=B;i++){
    if(i%K==0){
      ans++;
      break;
    }
  }
  if (ans==0)
    cout<<"NG"<<endl;
  else
    cout << "OK"<<endl;
  return 0;
}