#include<iostream>
using namespace std;

void solving(){
int k,a,b;
cin>>k>>a>>b;
int fl=1;
for(int i=a;i<=b;i++){
    if(i%k==0){fl=0;cout<<"OK\n";break;}
}
if(fl==1)cout<<"NG\n";
}
int main(){
    ios::sync_with_stdio(0);
    cin.tie(0);

    solving();
    return 0;
}