"use strict";
var __importDefault = (this && this.__importDefault) || function (mod) {
    return (mod && mod.__esModule) ? mod : { "default": mod };
};
Object.defineProperty(exports, "__esModule", { value: true });
var fs_1 = __importDefault(require("fs"));
var input = fs_1.default.readFileSync('/dev/stdin', 'utf8').split('\n');
var k = +input[0];
var a = +input[1].split(' ')[0];
var b = +input[1].split(' ')[1];
var result = 'NG';
for (var i = 0; i < 1000; i++) {
    if (a <= i * k && i * k <= b && result === 'NG') {
        result = 'OK';
    }
}
console.log(result);