#include <bits/stdc++.h>

#define rep(i,a,b) for(int i=a;i<b;i++)
#define drep(i,a,b) for(int i=a;i>=b;i--)
#define fore(i,a) for(auto &i:a)
#define all(x) (x).begin(),(x).end()
using namespace std;
void _main(); int main() { cin.tie(0); ios::sync_with_stdio(false); _main(); }
typedef long long ll; const int inf = INT_MAX / 2; const ll infl = 1LL << 60;
template<class T>bool chmax(T& a, const T& b) { if (a < b) { a = b; return 1; } return 0; }
template<class T>bool chmin(T& a, const T& b) { if (b < a) { a = b; return 1; } return 0; }

//---------------------------------------------------------------------------------------------------

void _main() {
    int K, A, B;
    cin >> K;
    cin >> A >> B;
    bool res = false;
    rep(i, A, B + 1) {
        if (i % K == 0) {
            res = true;
            break;
        }
    }
    if (res) cout << "OK" << endl;
    else cout << "NG" << endl;
}