#include <iostream>
using namespace std;

int main() {
    // prepare variables
    int multiplier, lb, ub;
    cin >> multiplier >> lb >> ub;
    bool is_achievable = false;

    // determines search upper boundary
    int ub_search = lb + multiplier - 1;
    ub_search = ub < ub_search ? ub : ub_search;
    for(int i = lb; i <= ub_search; ++i) {
        int mod = i%multiplier;
        if(mod == 0){
            is_achievable = true;
            break;
        }
    }

    if(is_achievable)
        cout << "OK" << endl;
    else
        cout << "NG" << endl;
    return 0;
}
