/*
Question:

*/

/*
Solution:
*/
#include <algorithm>
#include <iostream>
#include <vector>

using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vector<int>> vvi;
typedef pair<int, int> pi;

#define PB push_back
#define MP make_pair
// #define REP(i, begin, end) for (__typeof(end) i = (begin) - ((begin) > (end)); i != (end) - ((begin) > (end)); i += 1 - 2 * ((begin) > (end)))
#define REP(i, a, b) for (int i = a; i <= b; i++)
#define show(arr)                          \
    for (auto& ax : arr) cout << ax << ", "; \
    cout << "\n";
#define disp(x) cerr << #x << " is " << x << endl;

//One-char comment switch:
/*
commented
//*/

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    ll k, a, b;
    cin >> k >> a >> b;

    if (a % k == 0 || b % k == 0 || (a + (k-(a%k)) <= b))
        cout << "OK" << "\n";
    else
        cout << "NG" << "\n";
}
