// Slower C++ solution:
///_________________________________ B I S M I L L A H I R  R A H M A N I R  R A H I M __________________________________________________



#include<bits/stdc++.h>

using namespace std;



typedef bool                   boo;

typedef int                    li;

typedef long                   il;

typedef unsigned long          ul;

typedef long long int          ll;

typedef unsigned long long     ull;

typedef double                 dd;

typedef string                 str;



#define vli                    vector<li>

#define vll                    vector<ll>

#define sli                    set<li>

#define sll                    set<ll>

#define pli                    pair<li, li>

#define pll                    pair<ll, ll>

#define vpi                    vector<pair<li, li>>

#define vpl                    vector<pair<ll, ll>>

#define mpl                    map<ll, ll>



#define wt                     ll t; cin>>t; while(t--)

#define input(a,n)             for(int i=0;i<n;i++) cin>>a[i];

#define lp(a, i, b)            for(ll i=a; i<b; i++)

#define rlp(a, i, b)           for(ll i=a; i>=b; i--)

#define sz(x)                  x.size()

#define len(z)                 z.begin(), z.end()

#define ci(x)                  cin>>x;

#define co(x)                  cout<<x nl

#define fix(x)                 fixed<<setprecision(x)

#define mem(z, l)              memset(z, l, sizeof(z))

#define MP                     make_pair

#define pb                     push_back

#define F                      first

#define S                      second

#define nl                     <<endl

#define nll                    cout<<endl

#define sp                     <<" "<<

#define sl                     <<" "

#define cy                     cout<<"YES" nl

#define cn                     cout<<"NO" nl

#define rn                     return

#define good_bye               return 0

#define gcd(a,b)               __gcd(a,b)

#define lcm(a,b)               (a*(b/gcd(a,b)))

#define faster                 ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);

#define input_txt()            freopen("input.txt", "r", stdin); freopen("output.txt", "w", stdout);



const double eps =             1e-9;

const int inf =                2000000000;

const ll infLL =               9000000000000000000;

const ll MOD =                 1e+7;

//const double PI +               3.1415926536



int dx[] =                     {0, 0, +1, -1, +1, +1, -1, -1};

int dy[] =                     {+1, -1, 0, 0, +1, -1, +1, -1};

//ll Pow(ll P, ll Q)           { ll R=1; for(ll I=1; I<=Q; I++) R*=P; rn R; }

//ll fact(ll N)                { ll M=1; for(ll I=1; I<=N; I++) M*=I; return M; }

//void dfs(ll K)               { vis[K]=true; for(auto J: v[K]) { if(!vis[J]) dfs(J); } }

//void bfs(ll s)               { queue<ll>q; q.push(s); while(!q.empty()) { ll u=q.front(); q.pop(); for(auto i : v[u]) if(lev[i]==-1) { lev[i]=lev[u]+1; q.push(i); } } }

//void sieve(ll MX)            { S.pb(2); for(ll I=3; i<=MX; i+=2) { if(!vis[I]) { S.pb(I); for(ll J=I*I; j<=MX; J+=(2*I)) vis[J]=true; } } }

//bool isPrime(ll n)           { if(n%2==0) rn false; for(ll i=3; i*i<=n; i+=2) { if(n%i==0) rn false; } rn true; }



///_____________________________________________ L E T ' S  B E G I N __________________________________________________________________________



const int mX = 1e6+123;

ll n, m, k;



void case_i()

{

    ci(k>>n>>m);

    for(ll i=n; i<=m; i++) if(i%k==0) { cout<<"OK" nl; rn; }

    cout<<"NG" nl;

}



int main()

{

    faster;  //  input_txt();

    case_i();

    good_bye;

}



//                                                                                                          author : 5 A 1 F U D D 1 N  5 A 8 8 1 R



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// Faster C++ solution for the same problem (measured speedup: 5.389051622422093x):
#include <stdio.h>



int main(){

	int n;

	scanf("%d", &n);

	int T, K;

	scanf ("%d %d", &T, &K);

	

	for (int i = T; i <= K; i++){

		if (i % n == 0){

			puts("OK");

			return 0;

		}

		else continue;

	}

	puts("NG");

	return 0;

}