#include <iostream>
#include <algorithm>
#include <vector>
#include <cmath>
#include <string>
#include <map>

#define ll long long
#define REP(i,n) for(int i = 0; i < n; i++)
#define PI 3.141592653589
#define MOD 1000000007

using namespace std;

int gcd(int a, int b){return (a % b)? gcd(b, a % b) : b;}
int lcm(int a, int b){return a * b / gcd(a, b);}

void solve_A(){
    int k;
    cin >> k;
    int a, b;
    cin >> a >> b;

    bool flag = false;
    int i = 1;
    while(i* k <= b){
        if(a <= i*k && i*k <= b) flag = true;
        i++;
    }

    if(flag) cout << "OK";
    else cout << "NG";
}

int main(void){
    solve_A();
    
    return 0;
}