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

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