// #pragma GCC target("avx,avx2,fma")
// #pragma GCC optimization ("Ofast")
// #pragma GCC optimization ("unroll-loops")
#include<bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<int , int> pii;
typedef pair<ll, ll> pll;
typedef vector<pii> vii;
typedef vector<pll> vll;
#define mod 1000000007
#define rep(i, a, b) for(ll i = a; i < b; i++)
#define repc(i, a, b, c) for (ll i = a; (c > 0 ? i < b : i > b) and c != 0; i += c)
// #define mp make_pair
#define fi first
#define si second
#define pb push_back
#define all(name) name.begin(), name.end()
#define ral(name) name.rbegin(), name.rend()
#define fact(n) rep(i, 1, n+1)ft.pb((ft[i-1]*i)%mod)
#define mod_in(a) power(a, mod - 2)
#define ncr(n, r) (n>=r?((ft[n]*mod_in((ft[r]*ft[(n)-(r)])%mod))%mod):0LL)
#define deb(x) cerr << "[" << #x << " " << x << "]" << endl;
#define endl '\n'
// #define int ll
vector<ll> ft(1, 1LL);

/*======================================================================*/


void solve(){
    int a, b, k;
    cin >> k >> a >> b;
    rep(i, a, b+1){if(i%k == 0){cout << "OK";return;}}
    cout << "NG";
}
signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);cout.tie(NULL);
    int t = 1;
    //cin >> t;
    while(t--){
        solve();
    }
}