#include <bits/stdc++.h>
using namespace std;
long long T;
const long long M = 4e5 + 20;
long long n, m, k;
long long p[M];
inline long long kaf(long long a, long long b) { return a / b; }
inline long long saqf(long long a, long long b) { return (a + b - 1) / b; }
int32_t main() {
  ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
  cin >> T;
  while (T--) {
    cin >> n >> m >> k;
    for (long long i = 0; i < m; i++) cin >> p[i];
    p[m] = n;
    for (long long i = m; i > 0; i--) p[i] -= p[i - 1];
    long long D, U;
    long long low = 0, high = n + 1;
    while (high - low > 1) {
      long long mid = (low + high) / 2;
      long long sum = 0;
      for (long long i = 0; i <= m; i++) {
        if (p[i] < mid) {
          sum = -1;
          break;
        }
        sum += kaf(p[i], mid) - 1;
      }
      if (sum < k)
        high = mid;
      else
        low = mid;
    }
    D = low;
    low = 0, high = n + 1;
    while (high - low > 1) {
      long long mid = (low + high) / 2;
      long long sum = 0;
      for (long long i = 0; i <= m; i++) {
        sum += saqf(p[i], mid) - 1;
      }
      if (sum > k)
        low = mid;
      else
        high = mid;
    }
    U = high;
    vector<pair<long long, long long> > vec;
    for (long long i = 0; i <= m; i++) {
      long long v1 = saqf(p[i], U), v2 = kaf(p[i], D);
      if (v1 > v2) {
        long long x = kaf(p[i], v1);
        long long y = saqf(p[i], v2);
        vec.push_back({D - x, y - U});
      }
    }
    if (vec.empty()) {
      cout << U - D << '\n';
      continue;
    }
    long long ans = n + 5;
    sort(vec.begin(), vec.end());
    long long mx = 0;
    for (long long i = ((long long)vec.size()) - 1; i >= 0; i--) {
      ans = min(ans, vec[i].first + mx);
      mx = max(mx, vec[i].second);
    }
    ans = min(ans, mx);
    ans += U - D;
    cout << ans << '\n';
  }
}
