#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define int long long
#define double long double
#define x first
#define y second
#define pb push_back
using namespace std;
using pii=pair <int,int>;
using tii=pair <pii,int>;
using rii=pair <int,pii>;
using qii=pair <pii,pii>;
using namespace __gnu_pbds;
const int mod=998244353LL;
void solve(){
    int n,k;
    cin>>n>>k;
    int a[n+1];
    for (int i=1; i<=n; i++) cin>>a[i];
    for (int i=1; i<=n; i++) a[i]-=i;
    int l=1,r=n;
    while (l<r){
        int mid=(l+r+1)/2;
        bool ok=0;
        int sums=0,suml=0;
        multiset <int> sm,la;
        for (int i=1; i<=mid; i++){
            sm.insert(a[i]);
            sums+=a[i];
        }
        while (sm.size()>mid/2){
            auto it=(--sm.end());
            sums-=(*it);
            suml+=(*it);
            la.insert(*it);
            sm.erase(it);
        }
        if (suml-(int)la.size()*(*la.begin())+(int)sm.size()*(*la.begin())-sums<=k) ok=1;
        for (int i=2; i+mid-1<=n; i++){
            auto it=sm.find(a[i-1]);
            if (it!=sm.end()){
                sums-=a[i-1];
                sm.erase(it);
            } else {
                suml-=a[i-1];
                la.erase(la.find(a[i-1]));
            }
            if (a[i+mid-1]>=(*la.begin())){
                la.insert(a[i+mid-1]);
                suml+=a[i+mid-1];
            } else {
                sm.insert(a[i+mid-1]);
                sums+=a[i+mid-1];
            }
            while (sm.size()<mid/2){
                auto it=la.begin();
                sums+=(*it);
                suml-=(*it);
                sm.insert(*it);
                la.erase(it);
            }
            while (sm.size()>mid/2){
                auto it=(--sm.end());
                sums-=(*it);
                suml+=(*it);
                la.insert(*it);
                sm.erase(it);
            }
            if (suml-(int)la.size()*(*la.begin())+(int)sm.size()*(*la.begin())-sums<=k) ok=1;
        }
        if (ok) l=mid;
        else r=mid-1;
    }
    cout<<l<<'\n';
}
signed main(){
    ios_base::sync_with_stdio(0); cin.tie(0);
    int t=1;
    cin>>t;
    while (t--) solve();
}