#include <bits/stdc++.h>
using namespace std;
#define rep(i, x, y) for (int i = (x); i <= (y); i++)
#define per(i, x, y) for (int i = (x); i >= (y); i--) 
#define int long long
using ll = long long; using ull = unsigned long long;
inline int read() {
    char ch = getchar(); int s = 0, f = 1;
    while (!isdigit(ch)) {if (ch == '-') f = -1; ch = getchar();}
    while (isdigit(ch)) s = (s << 1) + (s << 3) + (ch ^ 48), ch = getchar();
    return s * f;
}
constexpr int N = 5e5 + 5, V = 1e9;
int n, K, a[N], rt;
struct node {
    int su, cnt, ls, rs;
} t[N << 5];
int tot;
void upd(int p, int x, int &id, int l = -n, int r = V) {
    if (!id) id = ++tot;
    t[id].su += x * p, t[id].cnt += x;
    if (l == r) return ;
    int mid = (l + r) >> 1;
    p <= mid ? upd(p, x, t[id].ls, l, mid) : upd(p, x, t[id].rs, mid + 1, r);
}
int X, Y, cX, cY;
int qry(int &id, int l = -n, int r = V) {
    if (l == r) return l * cX - X + Y - l * cY;
    int mid = (l + r) >> 1, L = X + t[t[id].ls].su, R = Y + t[t[id].rs].su;
    int cL = cX + t[t[id].ls].cnt, cR = cY + t[t[id].rs].cnt;
    if (mid * cL - L + R - mid * cR <= (mid + 1) * cL - L + R - (mid + 1) * cR) {
        Y = R, cY = cR; return qry(t[id].ls, l, mid);
    } else {
        X = L, cX = cL; return qry(t[id].rs, mid + 1, r);
    }
}
inline bool chk() {
    X = 0, Y = 0, cX = 0, cY = 0;
    // cerr << qry(rt) << endl;
    X = 0, Y = 0, cX = 0, cY = 0;
    return qry(rt) <= K;
}
inline void sol() {
    n = read(), K = read();
    rep (id, 1, tot) t[id].ls = t[id].rs = t[id].cnt = t[id].su = 0;
    tot = rt = 0;
    rep (i, 1, n) a[i] = read() - i;
    int r = 0; int ans = 0;
    rep (l, 1, n) {
        if (r + 1 < l) r = l - 1;
        else if (l > 1) upd(a[l - 1], -1, rt);
        while (r < n) {
            // cerr << l << ' ' << r << endl;
            r++; upd(a[r], 1, rt);
            if (!chk()) {
                upd(a[r], -1, rt);
                r--; break;
            }
        }
        ans = max(ans, r - l + 1);
    }
    cout << ans << "\n";
}
signed main() {
    ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
    int _ = read(); while (_--) sol();
    return 0;
}