#include <bits/stdc++.h>
using namespace std;
#define int long long
#define endl '\n'
#define close ios::sync_with_stdio(false), cin.tie(0), cout.tie(0)

const int N = 1e5 + 5;

int n, k, m;
vector<int> input;
int a[N];

struct SEG
{
#define lson id << 1
#define rson id << 1 | 1
    int sum;
    int sz;
} seg[N << 2];

int getIndex(int v)
{
    return lower_bound(input.begin(), input.end(), v) - input.begin() + 1;
}

void up(int id)
{
    seg[id].sum = seg[lson].sum + seg[rson].sum;
    seg[id].sz = seg[lson].sz + seg[rson].sz;
}

void build(int id, int l, int r)
{
    seg[id].sum = 0;
    seg[id].sz = 0;
    if (l == r)
        return;
    int mid = (l + r) >> 1;
    build(lson, l, mid);
    build(rson, mid + 1, r);
}

void change(int id, int l, int r, int x, int v, int le)
{
    if (l == r)
    {
        seg[id].sum += v;
        seg[id].sz += le;
        return;
    }
    int mid = (l + r) >> 1;
    if (x <= mid)
        change(lson, l, mid, x, v, le);
    else
        change(rson, mid + 1, r, x, v, le);
    up(id);
}

int querySum(int id, int l, int r, int ql, int qr)
{
    if (ql <= l && r <= qr)
        return seg[id].sum;
    int mid = (l + r) >> 1, res = 0;
    if (ql <= mid)
        res += querySum(lson, l, mid, ql, qr);
    if (qr > mid)
        res += querySum(rson, mid + 1, r, ql, qr);
    return res;
}

int querySz(int id, int l, int r, int ql, int qr)
{
    if (ql <= l && r <= qr)
        return seg[id].sz;
    int mid = (l + r) >> 1, res = 0;
    if (ql <= mid)
        res += querySz(lson, l, mid, ql, qr);
    if (qr > mid)
        res += querySz(rson, mid + 1, r, ql, qr);
    return res;
}

int findKth(int id, int l, int r, int index)
{
    if (l == r)
        return l;
    int mid = (l + r) >> 1;
    if (seg[lson].sz >= index)
        return findKth(lson, l, mid, index);
    else
        return findKth(rson, mid + 1, r, index - seg[lson].sz);
}

bool check(int len)
{
    build(1, 1, m);
    for (int i = 1; i <= len; i++)
    {
        change(1, 1, m, getIndex(a[i]), a[i], 1);
    }
    int index = findKth(1, 1, m, (len + 1) / 2);
    int nowMid = input[index - 1];
    int cnt = querySz(1, 1, m, 1, index) * nowMid - querySum(1, 1, m, 1, index) +
              querySum(1, 1, m, index, m) - querySz(1, 1, m, index, m) * nowMid;
    for (int i = 1; i + len <= n; i++)
    {
        change(1, 1, m, getIndex(a[i]), -a[i], -1);
        change(1, 1, m, getIndex(a[i + len]), a[i + len], 1);
        index = findKth(1, 1, m, (len + 1) / 2);
        nowMid = input[index - 1];
        int ans = querySz(1, 1, m, 1, index) * nowMid - querySum(1, 1, m, 1, index) +
                  querySum(1, 1, m, index, m) - querySz(1, 1, m, index, m) * nowMid;
        cnt = min(cnt, ans);
    }
    return cnt <= k;
}

void solved()
{
    cin >> n >> k;
    input.clear();
    for (int i = 1; i <= n; i++)
    {
        cin >> a[i];
        a[i] -= i;
        input.push_back(a[i]);
    }
    sort(input.begin(), input.end());
    input.erase(unique(input.begin(), input.end()), input.end());
    m = input.size();
    int l = 1, r = n, ans = 0;
    while (l <= r)
    {
        int mid = (l + r) >> 1;
        if (check(mid))
        {
            ans = mid;
            l = mid + 1;
        }
        else
        {
            r = mid - 1;
        }
    }
    cout << ans << endl;
}

signed main()
{
    close;
    int T;
    cin >> T;
    while (T--)
    {
        solved();
    }
    return 0;
}