#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define endl "\n"
const int mod = 1e9 + 7;
const int N = 1e6+ 5;
const int inf = 0x3f3f3f3f;


ll n, k;
ll a[N];
bool check(int x) {
	multiset<ll> s1, s2;
	ll sum = 1e18, l = 0, r = 0;
	for (int i = 1; i < x; i++) {
		s2.insert(a[i]);
		r += a[i];
	}
	for (int i = x; i <= n; i++) {
		if (s1.size() && a[i] < *s1.rbegin()) {
			s1.insert(a[i]); l += a[i]; 
			s2.insert(*s1.rbegin()); r += *s1.rbegin();
			l -= *s1.rbegin();s1.erase(*s1.rbegin());
		}
		else {
			s2.insert(a[i]);
			r += a[i];
		}
		while (s1.size() < s2.size() + 1) {
			auto it = *s2.begin();
			
			l += it; s1.insert(it);
			r -= it; s2.erase(it);
		}
		
		ll d = *s1.rbegin();
		ll cnt = r - s2.size() * d + d * s1.size() - l;
		
		sum = min(sum,cnt);
		
		if (a[i - x + 1] > d) {
			s2.erase(a[i - x + 1]);
			r -= a[i - x + 1];
		}
		else {
			s1.erase(a[i - x + 1]);
			l -= a[i - x + 1];
		}
	}
	
	if(sum <= k)
	return 1;
	return 0;
}
void solve() {
	cin >> n >> k;
	for (int i = 1; i <= n; i++) {
		cin >> a[i];
		a[i] -= i;
		
	}
	/*for(int i = 1; i <= n; i ++)
	cout << a[i] << ' ';
	cout << endl;*/
	
	int l = 1, r = n ,answer = 1;
	while (l <= r) {
		int mid = l + r >> 1;
		if (check(mid)) {
			l = mid + 1;
			answer = mid;
		}
		else  r = mid - 1;
	}
	cout << answer << endl;
}

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