#include<bits/stdc++.h>
#define int long long
#define pii pair<int,int>
#define pb push_back
#define ub upper_bound
#define lb lower_bound
#define all(x) x.begin(),x.end()
#define fast  ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
using namespace std;
signed main(){
    fast;
    int k;
    cin>>k;
    int a,b;
    cin>>a>>b;
    int q1 = a/k;
    int q2 = b/k;
    if(q1!=q2)
        cout<<"OK";
    else{
        if(a%k == 0){
            cout<<"OK";
        }
        else cout<<"NG";
    }
}
