N12789 - 도키도키 간식드리미

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
import java.util.StringTokenizer;
import java.util.Stack;

public class Main {
    static final BufferedReader BR = new BufferedReader(new InputStreamReader(System.in));
    static StringTokenizer ST;

    public static void main(String[] args) throws IOException{
        Integer.parseInt(BR.readLine());
        input();
    }

    private static void input() throws IOException {
        Stack<Integer> newLine = new Stack<>();
        int min = 0;
        int target;

        ST = new StringTokenizer(BR.readLine());

        while(ST.hasMoreTokens()) {
            target = Integer.parseInt(ST.nextToken());

            if(target == min+1) {
                min++;
            } else {
                while (!newLine.empty() && newLine.peek() == min + 1) {
                    min++;
                    newLine.pop();
                }
                newLine.add(target);
            }
        }
        if(newLine.empty())
            System.out.println("Nice");
        else if(newLine.peek() == min+1)
            System.out.println("Nice");
        else
            System.out.println("Sad");
    }
}