#include<bits/stdc++.h>

#define vc vector
#define pb emplace_back
#define pii pair<int, int>
#define mkp make_pair
#define rep(i, a, b) for(int i = (a); i <= (b); ++i)
#define lep(i, a, b) for(int i = (a); i >= (b); --i)

#define int long long

using namespace std;

inline int read() {
	int x = 0, w = 0; char ch = getchar(); while(!isdigit(ch)) w |= (ch == '-'), ch = getchar();
	while(isdigit(ch)) x = x * 10 + (ch ^ 48), ch = getchar(); return w ? -x : x; 
}

const int N = 5e5 + 5;

int n, k, len, ans, a[N], b[N], o[N];

namespace sgt {
	const pii emp = mkp(0, 0);
	int idx, rt[N], lc[N * 20], rc[N * 20];
	pii tre[N * 20];
	pii operator + (pii A, pii B) { return mkp(A.first + B.first, A.second + B.second); } 
	pii operator - (pii A, pii B) { return mkp(A.first - B.first, A.second - B.second); }
	#define mid (l + r >> 1)
	inline int newnode() { ++idx; lc[idx] = rc[idx] = 0; tre[idx] = emp; return idx; }
	inline void ins(int &k, int pr, int l, int r, int p, pii v) {
		k = newnode(); lc[k] = lc[pr], rc[k] = rc[pr]; tre[k] = tre[pr] + v;
		if(l != r) return p <= mid ? ins(lc[k], lc[pr], l, mid, p, v) : ins(rc[k], rc[pr], mid + 1, r, p, v);
	}
	inline int kth(int x, int y, int l, int r, int k) {
		if(l == r) return l; 
		int tot = tre[lc[x]].first - tre[lc[y]].first;
		return tot >= k ? kth(lc[x], lc[y], l, mid, k) : kth(rc[x], rc[y], mid + 1, r, k - tot);
	}
	inline pii ask(int x, int y, int l, int r, int L, int R) {
		if(!x || L > R) return emp;
		if(L <= l && R >= r) return tre[x] - tre[y];
		if(L > mid) return ask(rc[x], rc[y], mid + 1, r, L, R);
		if(R <= mid) return ask(lc[x], lc[y], l, mid, L, R);
		return ask(lc[x], lc[y], l, mid, L, R) + ask(rc[x], rc[y], mid + 1, r, L, R);
	}
}
using namespace sgt;

inline int calc(int l, int r) {
	int k = (r - l + 2) / 2, x = kth(rt[r], rt[l - 1], 1, len, k);
	auto u = ask(rt[r], rt[l - 1], 1, len, 1, x);
	auto v = ask(rt[r], rt[l - 1], 1, len, x + 1, len);
	return u.first * b[x] - u.second + v.second - v.first * b[x];
}

inline int check(int l, int r) {
	if(r > n) return 0;
	return calc(l, r) <= k;
}

inline void testcase() {
	n = read(); k = read(); len = idx = 0; ans = 1;
	rep(i, 1, n) b[++len] = a[i] = read() - i, o[i] = i;
	
	sort(b + 1, b + 1 + len); len = unique(b + 1, b + 1 + len) - b - 1;
	rep(i, 1, n) {
		a[i] = lower_bound(b + 1, b + 1 + len, a[i]) - b;
		ins(rt[i], rt[i - 1], 1, len, a[i], mkp(1, b[a[i]]));
	}
	
	random_shuffle(o + 1, o + 1 + n);
	for(int i = 1, u = o[1], l, r; i <= n; i++, u = o[i]) {
		if(!check(u, u + ans - 1)) continue;
		l = 1; r = n - u + 1;
		while(l <= r) 
			if(check(u, u + mid - 1)) l = mid + 1;
			else r = mid - 1;
		ans = max(ans, r);
	}
	
	printf("%lld\n", ans);
}

signed main() {
	srand(time(0));
	int t = read(); while(t--) testcase();
	return 0;
}