#include <bits/stdc++.h>
#define pii pair<int, int>
#define pll pair<long long, long long>
#define pdd pair<double, double>
#define vi vector<int>
#define vll vector<long long>
#define vpii vector<pair<int, int>>
#define vpll vector<pair<long long, long long>>
#define vpdd vector<pair<double, double>>
#define mp make_pair
#define fi first
#define se second
#define all(v) v.begin(), v.end()
#define pb push_back
#define endl "\n"
#define vvi vector<vector<int>>
#define vvll vector<vector<long long>>

using namespace std;
using LL = long long;
using ULL = unsigned long long;
const int N = 5e5 + 10, INF = 0x3f3f3f3f, mod = 998244353;
const LL bigINF = ((ULL)(1) << 63) - 1;
const double eps = 1e-6;
LL n, k;
vll a(N);

bool check(int x) {
    multiset<int> lo, hi;
    LL minus = 0, plus = 0;
    for (int i = 1; i < x; ++i)
    {
        lo.insert(a[i]);
        minus += a[i];
    }
    while (hi.size() < (x - 1) / 2)
    {
        int tmp = *--lo.end();
        minus -= tmp;
        plus += tmp;
        hi.insert(tmp);
        lo.erase(--lo.end());
    }
    for (int i(x); i <= n; ++i)
    {
        if (lo.size() <= hi.size())
        {
            plus += a[i];
            hi.insert(a[i]);
            int mid = *hi.begin();
            hi.erase(hi.begin());
            lo.insert(mid);
            plus -= mid;
            minus += mid;
        }
        else
        {
            minus += a[i];
            lo.insert(a[i]);
            int mid = *--lo.end();
            lo.erase(--lo.end());
            hi.insert(mid);
            minus -= mid;
            plus += mid;
        }
        LL mid = *--lo.end();
        if (lo.size() * mid - minus + plus - hi.size() * mid <= k)
            return true;
        int old = a[i - x + 1];
        if (old <= *--lo.end())
        {
            minus -= old;
            lo.erase(lo.lower_bound(old));
        }
        else
        {
            plus -= old;
            hi.erase(hi.lower_bound(old));
        }
    }
    return false;
}

void Sol()
{
    
    cin >> n >> k;
    for(int i(1); i<= n; ++ i) {
        cin >> a[i];
        a[i] -= i;
    }
    int l = 1, r = n;

    while(l < r) {
        int mid = l + r + 1 >> 1;
        if(check(mid)) {
            l = mid;
        } else
            r = mid - 1;
    }
    cout << l << endl;
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr), cout.tie(nullptr);

    int t = 1;
    cin >> t;
    while (t--)
    {
        Sol();
    }

    return 0;
}