#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i, n) for(int i = 0; i < (int)(n); i++)
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
template<typename T> using min_priority_queue = priority_queue<T, vector<T>, greater<T>>;
const ll INF = 1LL<<60;
const ll MOD = 1e9 + 7;


int main() {
    ll k,a,b;
    bool ok = false;
    cin >> k >> a >> b;
    for (ll i = a;i<=b;i++) {
        if (i%k==0) ok = true;
    }
    if (ok) cout << "OK" << endl;
    else cout << "NG" << endl;

}