#include <bits/stdc++.h>
using namespace std;
int dy[] = {1, -1, 0, 0, -1, 1, 1, -1};
int dx[] = {0, 0, 1, -1, 1, -1, 1, -1};
void file() {}
void fast() {
  std::ios_base::sync_with_stdio(0);
  cin.tie(NULL);
}
bool ok = 0;
long long val = pow(2, 32) - 1;
long long fastpow(long long x, long long p) {
  if (!p) return 1;
  long long sq = fastpow(x, p / 2);
  if (sq > val) {
    ok = 1;
    return 0;
  }
  sq *= sq;
  if (sq > val) {
    ok = 1;
    return 0;
  }
  if (p & 1) sq *= x;
  if (sq > val) {
    ok = 1;
    return 0;
  }
  return sq;
}
int main() {
  file();
  fast();
  int t;
  cin >> t;
  while (t--) {
    int n, k;
    cin >> n >> k;
    vector<int> v1(n);
    for (auto &x : v1) cin >> x;
    long long mn = INT_MAX;
    int ans;
    for (int i = 0; i + k < n; i++) {
      if (v1[i + k] - v1[i] < mn) {
        mn = v1[i + k] - v1[i];
        ans = (v1[i + k] + v1[i]) / 2;
      }
    }
    cout << ans << "\n";
  }
  return 0;
}
