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

const ll maxs = 1e5+5;
const ll lmaxs = 20;
ll mod = 1e9+7;
ll oo = 1e15;

#define IOS ios_base::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);
#define pb push_back
#define mp make_pair
#define ff first
#define ss second
#define I insert
#define endl '\n'

void pre(){
    
}

void solve(){
    ll k;
    cin >> k;
    ll a,b;
    cin >> a >> b;
    ll f= a/k*k;
    if(f < a)
        f += k;
    if(f >= a and f <= b)
        cout << "OK";
    else cout << "NG" ; 
}

int main(){
    IOS;
    pre();
    ll T = 1;
    //cin>>T;
    while(T--){
        solve();   
    }
    return 0;
}