import java.util.Scanner;

public class Braces {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String str = sc.nextLine();
		char[] braces = str.toCharArray();

		int count1 = 0; // counter for ()
		int count2 = 0; // counter for {}
		int count3 = 0; // counter for []

		boolean sup = true;

		int i = 0;
		while(true) {
			if(braces[i] == '(') {
				count1++;
			}
			if(braces[i] == ')') {
				count1--;
			}
			if(braces[i] == '{') {
				count2++;
			}
			if(braces[i] == '}') {
				count2--;
			}
			if(braces[i] == '[') {
				count3++;
			}
			if(braces[i] == ']') {
				count3--;
			}

			if (count1 < 0 || count2 < 0 || count3 < 0) {
				sup = false;
			}

			i++;

			if(i >= braces.length) break;
		}

		if(sup) {
			System.out.println("Ok");
		}
		else {
			System.out.println("Not ok");
		}
	}
}