Help me in solving KDELI problem

help
,
1

My issue

what is error in my logic
sort(a.rbegin(), a.rend());

    int s = 0;
    // Adjust l to be zero-indexed
    l = l - 1;
    
    while (l < n) {
        s += a[l];
        l += k;
    }
    cout << s << endl;

My code

#include <bits/stdc++.h>
using namespace std;

int main() {
    int t;
    cin >> t;
    while (t--) {
        int n, k, l;
        cin >> n >> k >> l;
        vector<int> a(n);
        for (int i = 0; i < n; i++) {
            cin >> a[i];
        }
        // Sort in descending order to get the highest deliciousness first
        sort(a.rbegin(), a.rend());
        
        int s = 0;
        // Adjust l to be zero-indexed
        l = l - 1;
        
        while (l < n) {
            s += a[l];
            l += k;
        }
        cout << s << endl;
    }
    return 0;
}

Problem Link: Maximum Deliciousness Practice Coding Problem