#include<bits/stdc++.h>
#define int long long
#define endl '\n'
using namespace std;
void solve()
{   
    int n,k;
    cin>>n>>k;
    vector<int> a(n+1);
    for(int i=1;i<=n;i++) cin>>a[i],a[i]-=i;
    // for(int i=1;i<=n;i++) cerr<<a[i]<<' ';
    // cerr<<endl;
    auto check=[&](int x)
    {
        if(x==1) return 1;
        multiset<int> small,big;
        int suma=0,sumb=0;
        auto insert=[&](int temp)
        {
            if(small.size()<=big.size())
            {
                small.insert(temp);
                suma+=temp;
                if(big.size() && *small.rbegin()>*big.begin())
                {
                    int x=*small.rbegin(),y=*big.begin();
                    small.erase(small.find(x));
                    suma-=x;
                    big.erase(big.find(y));
                    sumb-=y;
                    small.insert(y);big.insert(x);
                    suma+=y;sumb+=x;
                }
            }
            else
            {
                big.insert(temp);
                sumb+=temp;
                if(small.size() && *small.rbegin()>*big.begin())
                {
                    int x=*small.rbegin(),y=*big.begin();
                    small.erase(small.find(x));
                    suma-=x;
                    big.erase(big.find(y));
                    sumb-=y;
                    small.insert(y);big.insert(x);
                    suma+=y;sumb+=x;
                }
            }
        };
        auto del=[&](int temp)
        {
            if(small.size() && temp<=*small.rbegin()) small.erase(small.find(temp)),suma-=temp;
            else big.erase(big.find(temp)),sumb-=temp;
        };


        for(int i=1;i<=n;i++)
        {
            if(i<=x) insert(a[i]);
            else
            {
                del(a[i-x]);
                insert(a[i]);
            }
            if(i>=x)
            {
                int mid;
                if(x%2) mid=*small.rbegin();
                else mid=(*small.rbegin()+*big.begin())/2;
                // if(x==5) cerr<<mid<<' '<<suma<<' '<<sumb<<endl;
                int cha=sumb-(big.size()*mid)+(small.size()*mid)-suma;
                if(cha<=k) return 1;
            }
        }
        return 0;
    };



    int l=1,r=n+1;
    while(l<r)
    {
        int mid=l+r>>1;
        if(check(mid)) l=mid+1;
        else r=mid;
    }
    cout<<l-1<<endl;
}
signed main()
{
    cin.tie(0)->sync_with_stdio(0);
    int t=1;
    cin>>t;
    while(t--) solve();
    return 0;
}