#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define endl '\n'
#define ull unsigned long long
using PII = pair<int, int>;
using ld = long double;
const int N = 5e5 + 5, M = 1e9 + 7;
 
typedef __int128 lll;
istream &operator>>(istream &cin, lll &x) { x=0; static string s; cin>>s; for (char c:s) x=x*10+(c-'0'); return cin; }
ostream &operator<<(ostream &cout, lll x) { static char s[60]; int tp=1; s[0]='0'+(x%10); while (x/=10) s[tp++]='0'+(x%10); while (tp--) cout<<s[tp]; return cout; }
 
mt19937_64 rng{ chrono::steady_clock::now().time_since_epoch().count() };
 
ll n, k, a[N], s[N];
 
template <typename T>
struct Fen{
    int n;
    vector<T> a;   
    Fen(int n_ = 0) {
        init(n_);
    }
    void init(int n_) {
        n = n_;
        a.assign(n + 1, T{});
    }
    void add(int x, const T &v) {
        for (int i = x; i <= n; i += i & -i) {
            a[i] += v;
        }
    }
    T qry(int x) {
        T ans{};
        for (int i = x; i > 0; i -= i & -i) {
            ans += a[i];
        }
        return ans;
    }
    T qry(int l, int r) {
        return qry(r) - qry(l - 1);
    }
    int kth(const T &k) {
        int x = 0;
        T cur{};
        for (int i = 1 << __lg(n); i > 0; i /= 2) {
            if (x + i <= n && cur + a[x + i] < k) {
                x += i;
                cur += a[x];
            }
        }
        return x + 1;
    }
};
 
#define find(x) lower_bound(v.begin(), v.begin() + m - 1, x) - v.begin()+1
 
bool chk(int L) {
    vector<ll>v;
    for (int i = 1;i <= n;i++)v.push_back(a[i]);
    for (int i = 1;i + L - 1 <= n;i++) {
        ll res = s[i + L - 1] - s[i - 1];
        ll x = res / L, y = res / L + 1;
        v.push_back(x), v.push_back(y);
    }
    sort(v.begin(), v.end());
    int m = unique(v.begin(), v.end()) - v.begin();
    Fen<ll>t(m + 2);
    Fen<int>t2(m + 2);
    // lower_bound(v.begin(), v.begin() + m - 1, x) - v.begin()
    for (int i = 1;i < L;i++) {
        int x = find(a[i]);
        t.add(x, a[i]);
        t2.add(x, 1);
    }
    // for (int i = 0;i < m;i++)cout << v[i] << ' ';
    // cout << endl;
    // cout <<L<<' '<< 233 << ' ' << t2.qry(find(13)) << endl;
    for (int i = 1;i + L - 1 <= n;i++) {
        ll res = s[i + L - 1] - s[i - 1];
        int idx1 = find(a[i + L - 1]);
        t.add(idx1, a[i + L - 1]);
        t2.add(idx1, 1);
        int id = t2.kth((L + 1) / 2) - 1;
        ll x = v[id];
        ll y = v[id + 1];
        int idxx = find(x);
        // int idxy = find(y);
        int c1 = t2.qry(idxx);
        // int c2 = t2.qry(idxy);
        ll s1 = c1 * x - 2 * t.qry(idxx) + res - (L - c1) * x;
        // ll s2 = c2 * y - 2 * t.qry(idxy) + res - (L - c2) * y;
        if (s1 <= k)return 1;
        idx1 = find(a[i]);
        t.add(idx1, -a[i]);
        t2.add(idx1, -1);
    }
    return 0;
}
void solve() {
    cin >> n >> k;
    for (int i = 1;i <= n;i++) {
        cin >> a[i];
        a[i] += n - i;
        // cout << a[i] << " \n"[i == n];
        s[i] = s[i - 1] + a[i];
    }
    int l = 1, r = n;
    // cout << chk(4) << endl;
    while (l < r) {
        int mid = l + r + 1 >> 1;
        if (chk(mid))l = mid;
        else r = mid - 1;
    }
    cout << l << endl;
}
 
signed main() {
    ios::sync_with_stdio(0), cin.tie(0);
    int tt = 1;
    // cout << fixed << setprecision(12);
    cin >> tt;
    while (tt--)solve();
}