// Problem : A - We Love Golf
// Contest : AtCoder - AtCoder Beginner Contest 165
// URL : https://atcoder.jp/contests/abc165/tasks/abc165_a
// Memory Limit : 1024 MB
// Time Limit : 2000 ms
// Powered by CP Editor (https://github.com/cpeditor/cpeditor)


#include <bits/stdc++.h>
using namespace std;
//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>
//using namespace __gnu_pbds;
// #include <boost/multiprecision/cpp_int.hpp>
// using namespace boost::multiprecision;

//methods: find_by_order(k); & order_of_key(k);
//To make it an ordered_multiset, use pairs of (value, time_of_insertion)
//to distinguish values which are similar

#define int long long
#define pii pair<int,int>
#define pb push_back
template < typename T >
ostream &operator << ( ostream & os, const vector< T > &v ) {
            os << "{";
                for(auto it = v.begin(); it != v.end(); ++it) {
                                if( it != v.begin() ) os << ", ";
                                        os << *it;
                                            }
                    return os << "}";

}
#define vi vector<int>
#define ed end()
#define bg begin()
template < typename F, typename S >
ostream& operator << ( ostream& os, const pair< F, S > & p ) {
            return os << "(" << p.first << ", " << p.second << ")";
}
#define sz size()

template < typename T >
ostream &operator << ( ostream & os, const set< T > &v ) {
            os << "[";
                for(auto it = v.begin(); it != v.end(); ++it) {
                                if( it != v.begin() ) os << ", ";
                                        os << *it;
                                            }
                    return os << "]";
}
#define ln length()
#define all(x) x.begin(),x.end()
#define endl "\n"
#define NL cout<<'\n';
#define F first
#define S second
template < typename T >
ostream &operator << ( ostream & os, const multiset< T > &v ) {
            os << "[";
                for(auto it = v.begin(); it != v.end(); ++it) {
                                if( it != v.begin() ) os << ", ";
                                        os << *it;
                                            }
                    return os << "]";
}
#define disp(x) for(auto t : x )cout<<t<<" ";
#define for0(n) for(int i=0;i<n;i++)
#define for0j(n) for(int j=0;j<n;j++)
#define SS <<" "<<
#define arrin(a,n) vi a(n);for0(n){cin>>a[i];}
#define pf(x) cout<<x<<endl;
#define Check pf("Check")
#define gridin(num,n,m) for0(n){for0j(m) cin>>num[i][j];}
#define dispgrid(num,n,m) for0(n){for0j(m) cout<<num[i][j]<<" "; cout<<endl;}
template < typename F, typename S >
ostream &operator << ( ostream & os, const map< F, S > &v ) {
            os << "[";
                for(auto it = v.begin(); it != v.end(); ++it) {
                                if( it != v.begin() ) os << ", ";
                                        os << it -> first << " = " << it -> second ;
                                            }
                    return os << "]";
}
#define tkst(x) string x;cin >> x;
#define tk(a) int a;cin>>a;
#define tk2(a,b)tk(a)tk(b)
#define tk3(a,b,c)tk2(a,b)tk(c)
#define tk4(a,b,c,d)tk2(a,b)tk2(c,d)
#define tk5(a,b,c,d,e)tk4(a,b,c,d)tk(e)
#define tk6(a,b,c,d,e,f)tk3(a,b,c)tk3(d,e,f)
#define tk7(a,b,c,d,e,f,g)tk6(a,b,c,d,e,f)tk(g)
#define tk8(a,b,c,d,e,f,g,h)tk7(a,b,c,d,e,f,g)tk(h)
#define YES cout<<"YES"<<endl;
#define Yes cout<<"Yes"<<endl;
#define NO cout<<"NO"<<endl;
#define No cout<<"No"<<endl;
#define yes cout<<"yes"<<endl;
#define no cout<<"no"<<endl;
#define vpii vector<pii>
#define acum accumulate
#define fmap gp_hash_table
#define LONG LLONG
const int MOD=1000000007;
const int N=100000;



vector<string> vec_splitter(string s) {
	s += ',';
	vector<string> res;
	while(!s.empty()) {
		res.push_back(s.substr(0, s.find(',')));
		s = s.substr(s.find(',') + 1);
	}
	return res;
}

void debug_out(
vector<string> __attribute__ ((unused)) args,
__attribute__ ((unused)) int idx,
__attribute__ ((unused)) int LINE_NUM) { cerr << endl; }


template <typename Head, typename... Tail>
void debug_out(vector<string> args, int idx, int LINE_NUM, Head H, Tail... T) {
	if(idx > 0) cerr << ", "; else cerr << "Line(" << LINE_NUM << ") =  ";
	stringstream ss; ss << H;
	cerr << args[idx] << " = " << ss.str();
	debug_out(args, idx + 1, LINE_NUM, T...);
}

#ifndef ONLINE_JUDGE
#define db(...) debug_out(vec_splitter(#__VA_ARGS__), 0, __LINE__, __VA_ARGS__)
#endif

// To find number of elements less than k in array a
// answer would be int res = upper_bound(all(a),k) - a.bg

// To find number of elements greater than k in array a
// answer would be int res = a.ed - upper_bound(all(a),k)


int32_t main(){
	ios_base::sync_with_stdio(false);cin.tie(0);
	tk3(k,a,b)
	for(int i=a;i<=b;i++){
		if(i%k==0){
			pf("OK")
			return 0;
		}
	}
	pf("NG")
	return 0;
}


Measured memory_bytes: 3640