import java.util.*;

public class DanDiaoStack{

private Stack<Integer> stack;

private int[] arr;

public DanDiaoStack(int[] _arr){

stack=new Stack<Integer>();

arr = _arr;

}

public int[][] getResult(){

int[][] result = new int[arr.length][2];

for (int i=0; i<arr.length;i++ ) {

if(stack.isEmpty()){

stack.push(i);

}else{

while(!stack.isEmpty()){

if(arr[stack.peek()] > arr[i]){

break;

}

int cur = stack.pop();

result[cur][0] = stack.isEmpty() ? -1:stack.peek();

result[cur][1] = i;

}

stack.push(i);

}

}

while(!stack.isEmpty()){

int cur = stack.pop();

result[cur][0] = stack.isEmpty() ? -1:stack.peek();

result[cur][1] = -1;

}

return result;

}

public static void main(String[] args){

int[] arr= new int[]{2,3,5,1,6,0,7,9};

DanDiaoStack dan=new DanDiaoStack(arr);

int[][] result = dan.getResult();

for (int i=0; i<result.length;i++ ) {

for (int j=0; j<result[i].length; j++) {

System.out.print(result[i][j]+",");

}

System.out.println();

}

}

}