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

int main()
{
    int k, a, b; cin >> k >> a >> b;
    int c;
    c = (a + k)/k;
    if ( c*k <= b || k == 1) {
        cout << "OK" << endl;
    }else{
        cout << "NG" << endl;
    }

    return 0;
}
