#include<bits/stdc++.h>
#define Heap_PII priority_queue<PII, vector<PII>, greater<PII>>
#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define _for(i, a, b) for(int i = (a); i <= (b); i++)
#define _rep(i, a, b) for(int i = (a); i >= (b); i--)
#define out(x) cout << ((x) ? "YES" : "NO") << endl
#define mod(x, P) (((x) % (P) + (P)) % (P))
#define ULL unsigned long long
#define PII pair<int, int>
#define PLL pair<LL, LL>
#define lowbit(x) (x & -x)
#define LL long long
#define pb push_back
#define gcd __gcd
#define Big __int128
#define endl "\n"
#define x first
#define y second
#define int LL
using  namespace std;

const int N = 5e5 + 10, M = 1e4 + 10, INF = 1e9, P = 13331;

int n, m;
struct node{
	int l, r;
	int v, sum;
	void init(){
		l = r = v = sum = 0;
	}
}tr[N * 40];
int root, a[N], idx;

void pushup(int u){
	tr[u].v = tr[tr[u].l].v + tr[tr[u].r].v;
	tr[u].sum = tr[tr[u].l].sum + tr[tr[u].r].sum;
}
void modify(int &u, int l, int r, int x, int c){
	if(!u) tr[u = ++idx].init();
	if(l == r) tr[u].v += c, tr[u].sum += l * c;
	else{
		int mid = l + r >> 1;
		if(x <= mid) modify(tr[u].l, l, mid, x, c);
		else modify(tr[u].r, mid + 1, r, x, c);
		pushup(u);
	}
}
int sum(int u, int l, int r, int L, int R){
	if(!u) return 0;
	if(L <= l && r <= R) return tr[u].v;
	int mid = l + r >> 1, ans = 0;
	if(L <= mid) ans += sum(tr[u].l, l, mid, L, R);
	if(R > mid) ans += sum(tr[u].r, mid + 1, r, L, R);
	return ans;
}
int SUM(int u, int l, int r, int L, int R){
	if(!u) return 0;
	if(L <= l && r <= R) return tr[u].sum;
	int mid = l + r >> 1, ans = 0;
	if(L <= mid) ans += SUM(tr[u].l, l, mid, L, R);
	if(R > mid) ans += SUM(tr[u].r, mid + 1, r, L, R);
	return ans;
}
int query(int u, int l, int r, int k){
	if(l == r) return l;
	int mid = l + r >> 1;
	if(tr[tr[u].l].v < k) return query(tr[u].r, mid + 1, r, k - tr[tr[u].l].v);
	return query(tr[u].l, l, mid, k);
}
void solve(){
	cin >> n >> m;
	_for(i, 1, n) cin >> a[i];
	_for(i, 1, n) a[i] += 1e15 - i;
	root = 0;
	
	int L = 1, ans = 0;
	while(L <= n){
		int R = L + 1;
		modify(root, 0, 2e15, a[L], 1);
		while(R <= n){
			modify(root, 0, 2e15, a[R], 1);
			int l = query(root, 0, 2e15, (R - L) / 2 + 1);
			int t = sum(root, 0, 2e15, 0, l) * l - SUM(root, 0, 2e15, 0, l) + SUM(root, 0, 2e15, l, 2e15) - sum(root, 0, 2e15, l, 2e15) * l;
			if(t > m) break;
			R++;
		}
		ans = max(ans, R - L);
		L = R;
		root = 0;
	}
	cout << ans << endl;
}
signed main(){
	IOS;

	int T = 1;
	cin >> T;
	while(T--){
		solve();
	}
	return 0;
}

/*

1
7 5
7 2 5 5 4 11 7


*/