定義輔助棧分別儲存最大值、最小值。

import java.util.Scanner;
import java.util.Stack;


public class Test {

	public static class myStack {
	 Stack <Integer> dataStk = new Stack<Integer>();
	    Stack <Integer> minStk = new Stack<Integer>();
	    Stack <Integer> maxStk = new Stack<Integer>();
	    public void push(int node) {
	        dataStk.push(node);
	        if(minStk.isEmpty() || minStk.peek()>node){
	            minStk.push(node);
	        }else{
	            minStk.push(minStk.peek());
	        }
	        if(maxStk.isEmpty() || maxStk.peek()<node){
	        	maxStk.push(node);
	        }else{
	        	maxStk.push(maxStk.peek());
	        }
	    }
	    
	    public void pop() {
	        dataStk.pop();
	        minStk.pop();
	        maxStk.pop();
	    }
	    
	    public int top() {
	        return dataStk.peek();
	    }
	    
	    public int min() {
	        return minStk.peek();
	    }
	    public int max() {
	        return maxStk.peek();
	    }
	}
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc=new Scanner(System.in);
		int n=sc.nextInt();
		int arr[]=new int[n];
		myStack mystk = new myStack();
		for(int i=0;i<n;i++){
		arr[i]=sc.nextInt();
			mystk.push(arr[i]);
		}
		mystk.pop();
		System.out.println(mystk.max()+","+mystk.min());	
	}

}