how to sort by second value where first must be small in cpp code example

Example 1: c++ sort array of ints

// C++ program to demonstrate default behaviour of 
// sort() in STL. 
#include <bits/stdc++.h> 
using namespace std; 
  
int main() 
{ 
    int arr[] = {1, 5, 8, 9, 6, 7, 3, 4, 2, 0}; 
    int n = sizeof(arr)/sizeof(arr[0]); 
  
    sort(arr, arr+n); 
  
    cout << "\nArray after sorting using "
         "default sort is : \n"; 
    for (int i = 0; i < n; ++i) 
        cout << arr[i] << " "; 
  
    return 0; 
}

Example 2: stl sort in c++

sort(arr, arr+n, greater<int>()); // sorts in descending order