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

int main(){
    int K;
    cin >> K;
    int A,B;
    cin >> A >> B;

    int judge = 0;

    for(int i=A;i<=B;i++) {
        if(i%K==0) {
            judge = 1;
            break;
        }
    }

    if(judge==1) {
        cout << "OK" << endl;

    } else {
        cout << "NG" << endl;
    }
}