#include<bits/stdc++.h>
using namespace std;

#define endl '\n'
#define ll long long
#define ii pair<int,int>
#define vi vector<int>
#define vii vector<ii>
#define vvi vector<vi>
#define add push_back
#define MAXN 200005

int main(){ios_base::sync_with_stdio(false);
    
    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;

    return 0;
}
