#define F_C
#include <bits/stdc++.h>
#define rep(i, l, r) for(int i = l; i < r; i++)
#define hrp(i, l, r) for(int i = l; i <= r; i++)
#define rev(i, r, l) for(int i = r; i >= l; i--)
#define int ll
using namespace std;
typedef long long ll;
template<typename tn = int> tn next(void) { tn k; cin>>k; return k; }
#ifndef LOCAL
#define D(...) 0
#endif
const int U = 1e6;
const int kInf = 1e17;
int w[U], n, k, sum[U];
std::multiset<int> a, b;
int suma, sumb;
void init() {
  suma = sumb = 0;
  a.clear(), b.clear();
  a.insert(-kInf), b.insert(kInf);
}
void adjust() {
  while (a.size() > b.size() + 1) {
    std::multiset<int>::iterator it = (--a.end());
    b.insert(*it);
    a.erase(it);
    sumb += *it;
    suma -= *it;
  }
  while (b.size() > a.size()) {
    std::multiset<int>::iterator it = b.begin();
    a.insert(*it);
    b.erase(it);
    suma += *it;
    sumb -= *it;
  }
}
void add(int val_) {
  if (val_ <= *b.begin()) a.insert(val_), suma += val_;
  else b.insert(val_), sumb += val_;
  adjust();
}
void del(int val_) {
  std::multiset<int>::iterator it = a.lower_bound(val_);
  if (it != a.end()) {
    a.erase(it);
    suma -= *it;
  } else {
    it = b.lower_bound(val_);
    b.erase(it);
    sumb -= *it;
  }
  adjust();
}
int get_middle() {
  return *a.rbegin();
}
bool check(int len)
{
    init();
    hrp(i, 1, len) add(w[i]);
    int p1 = get_middle(), ans = (int)(((a.size()-1)*p1-suma)+(sumb-(b.size()-1)*p1));
    hrp(i, 1, n-len)
    {
        del(w[i]); add(w[i+len]);
        int p = get_middle();
        ans = min(ans, (int)(((a.size()-1)*p-suma)+(sumb-(b.size()-1)*p)));
    }
    return ans <= k;
}
signed main(void)
{
    #ifdef LOCAL
//	freopen("C:\\Users\\Loxil\\Desktop\\IN.txt", "r", stdin);
//	freopen("C:\\Users\\Loxil\\Desktop\\OUT.txt", "w", stdout);
    #endif
    
    ios::sync_with_stdio(false);
    cin.tie(0);
    
    int T = next();
    while(T--)
    {
        cin>>n>>k;
        hrp(i, 1, n) cin>>w[i], w[i] += n-i;

        int l = 1, r = n, ans = 1;
        while(l <= r)
        {
            int mid = l+r>>1;
            if (check(mid)) ans = max(ans, mid), l = mid+1;
            else r = mid-1;
        }
        cout<<ans<<endl;
    }
    
    return 0;
}
/*
1
6
202647942
268792718
 46761498
443917727
 16843338
125908043
191952768
 */