#include<bits/stdc++.h>
#define F(i, a, b) for(int i = a; i <= b; i ++)
#define Fd(i, a, b) for(int i = a; i >= b; i --)
#define int long long
#define pii pair<int, int>
#define fi first
#define se second
using namespace std;

const int N = 5e5 + 10;
const int inf = 1e18;

int n, a[N], m;

void sol() {
    cin >> n >> m;
    F(i, 1, n) cin >> a[i];
    F(i, 1, n) a[i] -= i;
    // F(i, 1, n) cout << a[i] << " \n" [i == n];
    multiset<int> s1, s2;
    int res = 0, sum1 = 0, sum2 = 0;
    for(int l = 1, r = 0; l <= n && r <= n; l ++) {
        if(l != 1) {
            int mm = s1.size() ? *s1.rbegin() : -inf;
            if(a[l - 1] <= mm) s1.erase(s1.find(a[l - 1])), sum1 -= a[l - 1];
            else s2.erase(s2.find(a[l - 1])), sum2 -= a[l - 1];
        }

        int sz1 = (r - l + 2) / 2, sz2 = r - l + 1 - sz1;
        while(s1.size() > sz1) {
            int now = *s1.rbegin(); sum1 -= now, sum2 += now;
            s1.erase(s1.find(now)), s2.insert(now);
        }
        while(s1.size() < sz1) {
            int now = *s2.begin(); sum1 += now, sum2 -= now;
            s2.erase(s2.find(now)), s1.insert(now);
        }
        int mm = s1.size() ? *s1.rbegin() : 0, ok = 0;
        if((mm * sz1) - sum1 + sum2 - (mm * sz2) <= m) res = max(res, r - l + 1);
        // cout << l << " " << r << " " << res << "\n";
        while(r < l) {
            ++ r;
            sz1 = (r - l + 2) / 2, sz2 = r - l + 1 - sz1;
            int tmp = s1.size() ? *s1.rbegin() : -inf;
            if(tmp > a[r]) s1.insert(a[r]), sum1 += a[r];
            else s2.insert(a[r]), sum2 += a[r];
            while(s1.size() > sz1) {
                int now = *s1.rbegin(); sum1 -= now, sum2 += now;
                s1.erase(s1.find(now)), s2.insert(now);
            }
            while(s1.size() < sz1) {
                int now = *s2.begin(); sum1 += now, sum2 -= now;
                s2.erase(s2.find(now)), s1.insert(now);
            }
            mm = *s1.rbegin();
            if((mm * sz1) - sum1 + sum2 - (mm * sz2) <= m) res = max(res, r - l + 1);
        }
        // cout << l << " " << r << " " << res << "\n";

        if((mm * sz1) - sum1 + sum2 - (mm * sz2) <= m) res = max(res, r - l + 1), ok = 1;
        if(ok) while(r < n) {
            ++ r;
            sz1 = (r - l + 2) / 2, sz2 = r - l + 1 - sz1;
            int tmp = s1.size() ? *s1.rbegin() : -inf;
            if(tmp > a[r]) s1.insert(a[r]), sum1 += a[r];
            else s2.insert(a[r]), sum2 += a[r];
            while(s1.size() > sz1) {
                int now = *s1.rbegin(); sum1 -= now, sum2 += now;
                s1.erase(s1.find(now)), s2.insert(now);
            }
            while(s1.size() < sz1) {
                int now = *s2.begin(); sum1 += now, sum2 -= now;
                s2.erase(s2.find(now)), s1.insert(now);
            }
            mm = *s1.rbegin();
            if((mm * sz1) - sum1 + sum2 - (mm * sz2) <= m) res = max(res, r - l + 1);
            else break;
            // if(r == 6) {
            //     cout << sum1 << " " << sum2 << "?\n";
            //     for(auto x : s1) cout << x << " "; cout << "\n";
            //     for(auto x : s2) cout << x << " "; cout << "\n";
            // }
        }
        // cout << l << " " << r << " " << res << "\n";
    }
    cout << res << "\n";
}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int t; cin >> t;
    F(i, 1, t) sol();
    return 0;
}
/*
5
7 5
7 2 5 5 4 11 7
6 0
100 3 4 5 99 100
5 6
1 1 1 1 1
5 50
100 200 300 400 500
1 100
3
*/