// step 1:

// make a vector

#include<bits/stdc++.h>

using namespace std;

int main(){

    vector<int> a(4) = {3,4,2,1};

// step 2:

// if you need sort

// if you need a[i]>a[i+1]

    sort(a.begin(),a.end(),great<int>());

// if you need a[i]<a[i+1]

    sort(a.begin(),a.end(),less<int>());

// if you need reverse

    reverse(a.begin(),a.end());

}