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

int main() {
 int K; int X; int Y; cin>>K>>X>>Y;
  int N=0;
  for(int i=X;i<Y+1; i++){
    if(i%K==0)
      N++;
    else continue;
  }
  if(N!=0) cout<<"OK"<<endl;
  else cout<<"NG"<<endl;
}