#pragma GCC optimize(3, "Ofast", "inline")
#include <iostream>
#include <bits/stdc++.h>
#define IOS ios::sync_with_stdio(false), cin.tie(0), cout.tie(0)
#define INF 0x3f3f3f3f
#define L_INF 0x7f3f3f3f3f3f3f3f
#define db cout << "debug\n";

using namespace std;
const int Mod = 998244353;
using ll = long long;
const int N = 5e5 + 10;
const int maxn = 5e5 + 10;
int n;
ll k;
ll a[N];
ll b[maxn];
ll prea[N];
int T[maxn], c[maxn * 30], lson[maxn * 30], rson[maxn * 30];
ll sum[maxn * 30], f[maxn];
int tot, t, r, l, m, q;
int build(int l, int r)
{
    int rt = tot++;
    sum[rt] = 0;
    c[rt] = 0;
    if (l != r)
    {
        int mid = (l + r) >> 1;
        lson[rt] = build(l, mid);
        rson[rt] = build(mid + 1, r);
    }
    return rt;
}

int update(int pre, int l, int r, int pos, int val)
{
    int rt = tot++;
    lson[rt] = lson[pre];
    rson[rt] = rson[pre];
    c[rt] = c[pre] + val;
    sum[rt] = sum[pre] + b[pos];
    if (l != r)
    {
        int mid = (l + r) >> 1;
        if (pos <= mid)
            lson[rt] = update(lson[pre], l, mid, pos, val);
        else
            rson[rt] = update(rson[pre], mid + 1, r, pos, val);
    }
    return rt;
}

ll query(int lr, int rr, int l, int r, int k)
{
    if (l == r)
        return b[l] * k;
    int rsum = c[rson[rr]] - c[rson[lr]];
    int mid = (l + r) >> 1;
    if (rsum >= k)
        return query(rson[lr], rson[rr], mid + 1, r, k);
    else
        return sum[rson[rr]] - sum[rson[lr]] + query(lson[lr], lson[rr], l, mid, k - rsum);
}

void init()
{
    sort(b + 1, b + 1 + n);
    m = unique(b + 1, b + 1 + n) - b - 1;
    T[0] = build(1, m);
    for (int i = 1; i <= n; ++i)
    {
        int pos = lower_bound(b + 1, b + 1 + m, a[i]) - b;
        T[i] = update(T[i - 1], 1, m, pos, 1);
    }
    for (int i = 1; i <= n; i++)
    {
        prea[i] = prea[i - 1] + a[i];
    }
}
int is_true(int l, int r)
{
    int len = r - l + 1;
    if (len & 1)
    {
        int kth = (r - l + 2) / 2;
        ll sumk = query(T[l - 1], T[r], 1, m, kth);
        ll sumk_1 = query(T[l - 1], T[r], 1, m, kth - 1);
        ll sum = prea[r] - prea[l - 1];
        // cout << sum << ' ' << sumk << ' ' << sumk_1 << ' ' << kth << '\n';
        // for (int i = 1; i <= n; i++)
        // {
        //     cout << a[i] << " \n"[i == n];
        // }
        return (sumk_1 - sum + sumk) <= k;
    }
    else
    {
        int kth = (r - l + 1) / 2;
        ll sumk = query(T[l - 1], T[r], 1, m, kth);
        ll sum = prea[r] - prea[l - 1];

        return (2LL * sumk - sum) <= k;
    }
}
int check(int len)
{
    for (int i = 1; i + len - 1 <= n; i++)
    {
        int l = i;
        int r = i + len - 1;
        if (is_true(l, r))
        {
            return 1;
        }
    }
    return 0;
}
void solve()
{
    cin >> n >> k;
    for (int i = 1; i <= n; i++)
    {
        cin >> a[i];
        a[i] = a[i] - i;
        b[i] = a[i];
    }
    int l = 1;
    int r = n;
    int ans = 1;
    init();

    // cout << check(1) << '\n';
    // cout << check(1) << '\n';
    // cout<<query
    // cout << check(5) << '\n';

    // cout << is_true(1, 6) << " " << is_true(2, 7) << '\n';
    while (l <= r)
    {
        // cout << l << " " << r << '\n';
        int mid = l + r >> 1;
        if (check(mid))
        {
            l = mid + 1;
            ans = mid;
        }
        else
        {
            r = mid - 1;
        }
    }
    cout << ans << '\n';
}
int main()
{
    IOS;
// freopen("in.txt", "r", stdin);
// freopen("out.txt", "w", stdout);
#ifndef ONLINE_JUDGE
    clock_t start_time = clock();
#endif
    int t = 1;
    cin >> t;
    while (t--)
    {
        solve();
    }
#ifndef ONLINE_JUDGE
    cout << "Used " << (double)(clock() - start_time) << " ms" << endl;
#endif
    return 0;
}