#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for (int (i)=(0);(i)<(int)(n);++(i))
using ll = long long;
using namespace std;

#define INF ((1<<30)-1)
#define LLINF (1LL<<60)
#define EPS (1e-10)

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