#include <bits/stdc++.h>
using namespace std;
template <class T>
T mceil(T a, T b) {
  if (a % b == 0)
    return a / b;
  else
    return a / b + 1;
}
const long long int M = 1e9 + 7;
const long long int N = 2e5 + 5;
const long long int inf = 9e18;
vector<long long int> vis;
vector<vector<long long int> > adj;
void solve() {
  long long int n, k;
  cin >> n >> k;
  vector<long long int> v(n);
  for (long long int i = 0; i < n; i++) cin >> v[i];
  if (k == 0) {
    cout << v[0] << "\n";
    return;
  }
  long long int x = -1;
  long long int mn = inf;
  for (long long int i = k; i < n; i++) {
    long long int a = v[i - k];
    long long int b = v[i];
    long long int x1 = (b + a) / 2;
    long long int mx1 = max(x1 - a, b - x1);
    if (mx1 < mn) {
      mn = mx1;
      x = x1;
    }
  }
  cout << x << "\n";
}
int main() {
  ios_base ::sync_with_stdio(false);
  cin.tie(NULL);
  long long int t;
  cin >> t;
  for (long long int i = 1; i < t + 1; i++) {
    solve();
  }
}
