#include <bits/stdc++.h>
using namespace std;
#define LL long long 
#define LLU long long unsigned
#define rarr(arr, n) for(int aab = 0; aab < n; aab++){cin >> arr[aab];}
#define parr(arr, n) for(int aab = 0; aab < n; aab++){cout << arr[aab] << " ";}
#define pb push_back
#define f first
#define s second
#define all(x) x.begin(), x.end()
#define debug(x) cout << #x << " = " << x << "\n";

#define freopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stdout);ios_base::sync_with_stdio(0);cin.tie(0);

int main(){
	int a, b, k;
	cin >> k >> a >> b;
	bool flag = false;
	for(int i = a; i <= b; i++){
		if(i % k == 0){
			flag = true;
		}
	}
	if(flag){
		cout << "OK";
	}
	else{
		cout << "NG";
	}
} 