#include <bits/stdc++.h>
#include <iterator>

#ifdef DYNAMIC_PIGEON
#include "algo/debug.h"
#else
#define debug(...) 114514
#endif

#define Dynamic_Pigeon 0

using i64 = std::int64_t;
using u64 = std::uint64_t;
using u32 = std::uint32_t;

constexpr i64 MOD = i64(1e9) + 7;
constexpr int INF = 1e9;
constexpr i64 INF_LONG_LONG = 1e18;

#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()


struct Node {
  std::multiset<int> l, r;
  i64 pre = 0, lst = 0;

  int get_mid() {
    return *l.rbegin();
  }

  void insert(int x) {
    if (l.empty() || x > *l.rbegin()) {
      r.insert(x);
      lst += x;
    } else {
      l.insert(x);
      pre += x;
    }

    if (r.size() + 1 < l.size()) {
      lst += *l.rbegin();
      pre -= *l.rbegin();
      r.emplace(l.extract(std::prev(l.end())).value());
    }

    if (l.size() < r.size()) {
      lst -= *r.begin();
      pre += *r.begin();
      l.emplace(r.extract(r.begin()).value());
    }
  }

  void erase(int x) {
    if (x > *l.rbegin()) {
      lst -= x;
      r.extract(x);
    } else {
      pre -= x;
      l.extract(x);
    }

    if (r.size() + 1 < l.size()) {
      lst += *l.rbegin();
      pre -= *l.rbegin();
      r.emplace(l.extract(std::prev(l.end())).value());
    }

    if (l.size() < r.size()) {
      lst -= *r.begin();
      pre += *r.begin();
      l.emplace(r.extract(r.begin()).value());
    }
  }

  void clear() {
    l.clear();
    r.clear();
    pre = 0;
    lst = 0;
  }
};


void tizzytyt_SuKi() {
  int n;
  i64 k;
  std::cin >> n >> k;
  std::vector<int> a(n + 1);
  for (int i = 1; i <= n; i++) {
    std::cin >> a[i];
    a[i] -= i;
  }

  Node m;

  auto check = [&](int len) -> bool {
    m.clear();
    for (int i = 1; i < len; i++) {
      m.insert(a[i]);
    }

    i64 res = INF_LONG_LONG;

    for (int i = len; i <= n; i++) {
      m.insert(a[i]);
      i64 mid = m.get_mid();
      i64 p = mid * i64(m.l.size()) - m.pre + m.lst - mid * i64(m.r.size());

      res = std::min(res, p);

      m.erase(a[i - len + 1]);
    }
    return res <= k;
  };

  int l = 1, r = n;
  while (l < r) {
    int mid = (l + r + 1) >> 1;
    if (check(mid)) {
      l = mid;
    } else {
      r = mid - 1;
    }
  }
  std::cout << l << "\n";
}

signed main() {
#ifdef DYNAMIC_PIGEON
  freopen("input.in", "r", stdin);
#else
  std::cin.tie(0)->sync_with_stdio(0);
#endif
  int t = 1;
  std::cin >> t;
  while (t--) {
    tizzytyt_SuKi();
  }
  return Dynamic_Pigeon;
}