#include <bits/stdc++.h>
using namespace std;
template <typename T>
ostream &operator<<(ostream &os, const vector<T> &v) {
  os << '{';
  string sep;
  for (const auto &x : v) os << sep << x, sep = ", ";
  return os << '}';
}
template <typename A, typename B>
ostream &operator<<(ostream &os, const pair<A, B> &p) {
  return os << '(' << p.first << ", " << p.second << ')';
}
void dbg_out() { cerr << endl; }
template <typename Head, typename... Tail>
void dbg_out(Head H, Tail... T) {
  cerr << ' ' << H;
  dbg_out(T...);
}
namespace IO {
const int BUFFER_SIZE = 1 << 15;
char input_buffer[BUFFER_SIZE];
int input_pos = 0, input_len = 0;
char output_buffer[BUFFER_SIZE];
int output_pos = 0;
char number_buffer[100];
uint8_t lookup[100];
void _update_input_buffer() {
  input_len = fread(input_buffer, sizeof(char), BUFFER_SIZE, stdin);
  input_pos = 0;
  if (input_len == 0) input_buffer[0] = EOF;
}
inline char next_char(bool advance = true) {
  if (input_pos >= input_len) _update_input_buffer();
  return input_buffer[advance ? input_pos++ : input_pos];
}
template <typename T>
inline void read_int(T &number) {
  bool negative = false;
  number = 0;
  while (!isdigit(next_char(false)))
    if (next_char() == '-') negative = true;
  do {
    number = 10 * number + (next_char() - '0');
  } while (isdigit(next_char(false)));
  if (negative) number = -number;
}
template <typename T, typename... Args>
inline void read_int(T &number, Args &...args) {
  read_int(number);
  read_int(args...);
}
void _flush_output() {
  fwrite(output_buffer, sizeof(char), output_pos, stdout);
  output_pos = 0;
}
inline void write_char(char c) {
  if (output_pos == BUFFER_SIZE) _flush_output();
  output_buffer[output_pos++] = c;
}
template <typename T>
inline void write_int(T number, char after = '\0') {
  if (number < 0) {
    write_char('-');
    number = -number;
  }
  int length = 0;
  while (number >= 10) {
    uint8_t lookup_value = lookup[number % 100];
    number /= 100;
    number_buffer[length++] = (lookup_value & 15) + '0';
    number_buffer[length++] = (lookup_value >> 4) + '0';
  }
  if (number != 0 || length == 0) write_char(number + '0');
  for (int i = length - 1; i >= 0; i--) write_char(number_buffer[i]);
  if (after) write_char(after);
}
void init() {
  bool exit_success = atexit(_flush_output) == 0;
  assert(exit_success);
  for (int i = 0; i < 100; i++) lookup[i] = (i / 10 << 4) + i % 10;
}
}  // namespace IO
const int64_t INF64 = (int64_t)2e18 + 5;
int64_t ceil_div(int64_t a, int64_t b) { return (a + b - 1) / b; }
int64_t N, K;
int M;
vector<int64_t> A;
int64_t minimum_cuts_to_stay_below(int64_t R) {
  int64_t sum = 0;
  for (int64_t &a : A) sum += (a - 1) / R;
  return sum;
}
int64_t maximum_cuts_to_stay_above(int64_t L) {
  int64_t sum = 0;
  for (int64_t &a : A) {
    if (a < L) return -INF64;
    sum += a / L - 1;
  }
  return sum;
}
void run_case() {
  IO::read_int(N, M, K);
  A.resize(M + 1);
  int64_t previous = 0;
  for (int i = 0; i < M; i++) {
    int64_t p;
    IO::read_int(p);
    A[i] = p - previous;
    previous = p;
  }
  A[M++] = N - previous;
  int64_t low = 1, high = N;
  while (low < high) {
    int64_t mid = (low + high) / 2;
    if (minimum_cuts_to_stay_below(mid) <= K)
      high = mid;
    else
      low = mid + 1;
  }
  int64_t R = low;
  low = 1;
  high = N;
  while (low < high) {
    int64_t mid = (low + high + 1) / 2;
    if (maximum_cuts_to_stay_above(mid) >= K)
      low = mid;
    else
      high = mid - 1;
  }
  int64_t L = low;
  assert(L <= R);
  vector<pair<int64_t, int64_t>> options;
  for (int64_t &a : A) {
    int64_t L_cuts = a / L - 1;
    int64_t my_R = ceil_div(a, L_cuts + 1);
    int64_t R_cuts = (a - 1) / R;
    int64_t my_L = a / (R_cuts + 1);
    my_L = min(my_L, L);
    my_R = max(my_R, R);
    options.emplace_back(my_L, my_R);
  }
  sort(options.begin(), options.end());
  int64_t best = INF64, max_R = R;
  for (pair<int64_t, int64_t> &option : options) {
    best = min(best, max_R - option.first);
    max_R = max(max_R, option.second);
  }
  IO::write_int(best, '\n');
}
int main() {
  IO::init();
  int tests;
  IO::read_int(tests);
  while (tests-- > 0) run_case();
}
