#include <bits/stdc++.h>   const int INF = (int)1e9 + 7;   int f(const std::vector<int> &arr, int k, int d) {     std::list<std::pair<int, int>> events, se;     for (auto &it : arr) {       events.push_back({it - d, 0});       se.push_back({it + d, 1});     }     events.merge(se);     int bal = 0;     for (auto it : events) {       bal += (it.second ? -1 : +1);       if (bal > k) {         return it.first;       }     }     return -INF;   }   int main() {     std::ios_base::sync_with_stdio(false);     std::cin.tie(0);     int t;     std::cin >> t;     while (t--) {       int n, k;       std::cin >> n >> k;       std::vector<int> arr(n);       for (auto &it : arr) {         std::cin >> it;       }       std::sort((arr).begin(), (arr).end());       int low = -1, high = (int)1e9;       while (high - low > 1) {         int mid = (low + high) / 2;         if (f(arr, k, mid) > -INF) {           high = mid;         } else {           low = mid;         }       }       std::cout << f(arr, k, high) <<   n ;     }     return 0;   }   