function main() {
	var i;
	let count = 0;
	let ans = 'NG';
	const arg = input.split(' ');
	const K = parseInt(arg[0], 10);
	const A = parseInt(arg[1], 10);
	const B = parseInt(arg[2], 10);
	for ( i = A; i < B+1; i++) {
		if ( i % K === 0) {
			count += 1;

		}
	}
	if (count > 0) {
		ans = 'OK';
	}
	console.log(ans);
}

main(require('fs').readFileSync('/dev/stdin', 'utf8'));