#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp> // Common file
#include <ext/pb_ds/tree_policy.hpp> // Including tree_order_statistics_node_update
#define int long long
#define pii pair<int, int>
#define all(a) a.begin(), a.end()
using namespace std;
using namespace __gnu_pbds;
using ordered_set = tree<pii, null_type, less<pii>, rb_tree_tag, tree_order_statistics_node_update>;


int INF = 1e18; 
const int MOD = 998244353;
const int N = 5e5 + 10;
const int LOG = 20;
const int dx[4] = {0, 0, 1, -1};
const int dy[4] = {1, -1, 0, 0};

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

int a[N];

void solve(){
    int n, k;
    cin >> n >> k;    

    for(int i = 1; i <= n; i++){
        cin >> a[i];
        a[i] = abs(a[i] - i);
    }

    int ans = 1;
    int l = 1, r = 1;

    multiset<int> L, R;
    int ltot = 0, rtot = 0;

    while(r <= n){
        L.insert(a[r]);
        ltot += a[r];

        int cost = INF;

        do{
            if(cost != INF){
                if(L.find(a[l]) != L.end()) L.erase(L.find(a[l])), ltot -= a[l];
                else if(R.find(a[l]) != R.end()) R.erase(R.find(a[l])), rtot -= a[l];
                l++;
            }

            if((int)L.size() - (int)R.size() > 1){
                ltot -= *L.rbegin();
                rtot += *L.rbegin();
                R.insert(*L.rbegin());
                L.erase(L.find(*L.rbegin()));
            }

            if((int)R.size() - (int)L.size() > 1){
                ltot += *R.begin();
                rtot -= *R.begin();
                L.insert(*R.begin());
                R.erase(R.find(*R.begin()));
            }

            while(!L.empty() && !R.empty() && *L.rbegin() > *R.begin()){
                int x = *L.rbegin(), y = *R.begin();
                ltot += y - x;
                rtot += x - y;

                L.erase(L.find(x)); L.insert(y);
                R.erase(R.find(y)); R.insert(x);
            }

            if(!L.empty()) cost = min(cost, (int)(*L.rbegin() * L.size() - ltot) + (int)(rtot - *L.rbegin() * R.size()));
            if(!R.empty()) cost = min(cost, (int)(*R.begin() * L.size() - ltot) + (int)(rtot - *R.begin() * R.size()));
            if(!L.empty() && !R.empty()){
                int m = (*R.begin() + *L.rbegin())/2;
                cost = min(cost, (int)(m * L.size() - ltot) + (int)(rtot - m * R.size()));
            }
        } while(cost > k);
        ans = max(ans, r - l + 1);
        r++;
    }

    cout << ans << '\n';
}


int32_t main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    
    int tt;
    cin >> tt;

    while(tt--){
        solve();
    }
}