//
// Created by 35263 on 2024/9/20.
//先减去index,然后再对顶堆求中位数，最后check所有值
#include <bits/stdc++.h>
#pragma GCC optimize(1)
#pragma GCC optimize(2)
#pragma GCC optimize(3,"Ofast","inline")
using namespace std;
typedef long long ll;
const int maxn = 500005;
const ll inf = 1e9+7;
int n,a[maxn];
ll k;
namespace Set{
    multiset<int>less,great;
    ll value_less,value_great;
    void init(){
        less.clear();great.clear();
        less.insert(-inf);great.insert(inf);
        value_less=0;value_great=0;
    }
    void adjust(){
        if(less.size()>great.size()+1){
            auto it=prev(less.end());
            value_great+=*it;value_less-=*it;
            great.insert(*it);less.erase(it);
        }
        if(less.size()<great.size()){
            auto it=great.begin();
            value_less+=*it;value_great-=*it;
            less.insert(*it);great.erase(it);
        }
    }
    void insert(int _val){
        if(_val<=*great.begin())less.insert(_val),value_less+=_val;
        else great.insert(_val),value_great+=_val;
        adjust();
    }
    void del(int _val){
        auto it=less.lower_bound(_val);
        if(it!=less.end()){
            less.erase(it);
            value_less-=_val;
        }
        else{
            it=great.lower_bound(_val);
            great.erase(it);
            value_great-=_val;
        }
        adjust();
    }
    int get_middle(){
        return *less.rbegin();
    }
    ll calc(int x){
        ll tmp_less=1ll*x*less.size()-value_less,tmp_great=1ll*value_great-1ll*x*great.size();
        return tmp_less+tmp_great;
    }
}
int check(int x){
    Set::init();
    for(int i=1;i<=x;i++){
        Set::insert(a[i]);
    }
    ll tmp=Set::calc(Set::get_middle());
    for(int i=x+1;i<=n;i++){
        Set::del(a[i-x]);
        Set::insert(a[i]);
        tmp=min(tmp,Set::calc(Set::get_middle()));
    }
    return tmp<=k;
}
void init(){
    cin>>n>>k;
    for(int i=1;i<=n;i++)cin>>a[i],a[i]-=i;
    int l=1,r=n,ans=0;
    while(l<=r){
        int mid=(l+r)>>1;
        if(check(mid)){
            ans=mid;l=mid+1;
        }
        else{
            r=mid-1;
        }
    }
    cout<<ans<<endl;
}
int main(){
    ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
    int t;
    cin>>t;
    while(t--){
        init();
    }
    return 0;
}