#include<bits/stdc++.h>
using namespace std;
int main()
  {
  int K,A,B,C;
  int ans=0;
  int a[1005];
  cin>>K;
  cin>>A>>B;
  C=A-B+1;
  for(int i=0;i<C;i++)
  for(int j=A;j<=B;j++)
  {
  	a[i]=j;
    if(a[i]%K==0)
      ans+=1;
    else
      ans+=0;
  }
  if(ans>0)
    cout<<"OK"<<endl;
  else
    cout<<"NG"<<endl;
  return 0;
}