#include <bits/stdc++.h>
using namespace std;
const int N = 5e5+10;
#define int long long 
#define PII pair<int,int>
struct node{
    int l,r,v,cnt;
}tr[N<<2];
int n,m;
void pushup(int i){
    auto &u=tr[i],&l=tr[i<<1],&r=tr[i<<1|1];
    u.v=l.v+r.v;
    u.cnt=l.cnt+r.cnt;
}
void build(int i,int l,int r){
    tr[i].l=l,tr[i].r=r,tr[i].cnt=0,tr[i].v=0;
    if(l==r){
        return;
    }
    int mid=l+r>>1;
    build(i<<1,l,mid);
    build(i<<1|1,mid+1,r);
    pushup(i);
}
void modify(int i,int x,int k,int k2){
    if(tr[i].l>=x&&tr[i].r<=x){
        auto &u=tr[i];
        u.v+=k;
        u.cnt+=k2;
        return;
    }
    if(tr[i].l>x||tr[i].r<x)return;
    if(tr[i<<1].r>=x)modify(i<<1,x,k,k2);
    if(tr[i<<1|1].l<=x)modify(i<<1|1,x,k,k2);
    pushup(i);
}
int query(int i,int f){
    if(tr[i].l==tr[i].r){
        return tr[i].l;
    }
    if(tr[i<<1].cnt>=f)return query(i<<1,f);
    else{
        return query(i<<1|1,f-tr[i<<1].cnt);
    }
}
PII query(int i,int l,int r){
    PII res={0,0};
    if(tr[i].l>=l&&tr[i].r<=r){
        auto &u=tr[i];
        return {u.v,u.cnt};
    }
    if(tr[i].l>r||tr[i].r<l)return res;
    if(tr[i<<1].r>=l){
        PII now= query(i<<1,l,r);
        res.first+=now.first;
        res.second+=now.second;
    }
    if(tr[i<<1|1].l<=r){
        PII now= query(i<<1|1,l,r);
        res.first+=now.first;
        res.second+=now.second;
    }
    return res;
}
void solve(){
    cin>>n>>m;
    vector<int>a(n+1);
    map<int,int>mp;
    vector<int>mpp(n+1);
    for(int i=1;i<=n;i++){
        cin>>a[i];
        a[i]-=i;
        mp[a[i]]++;
    }
    int idx=0;
    for(auto [pos,w]:mp){
        ++idx;
        mp[pos]=idx;
        mpp[idx]=pos;
    }
    int ans=1;
    build(1,1,n);
    for(int i=1,j=i;i<=n&&j<=n;i++){
        while(j<=n) {
            modify(1, mp[a[j]], a[j], 1);
            int mid = j - i + 1;
            int z = mpp[query(1, (mid+1)/2)];
            auto[lv, lcnt]=query(1, 1, mp[z]);
            auto[rv, rcnt]=query(1, mp[z] + 1, idx);
            if (lcnt * z - lv + rv - rcnt * z <= m){
                ans = max(ans, mid);
                j++;
            }else {
                modify(1, mp[a[i]], -a[i], -1);
                modify(1, mp[a[j]], -a[j], -1);
                break;
            }
        }
    }
    cout<<ans<<'\n';
}
signed main(){
    ios::sync_with_stdio(false);cin.tie(nullptr);
    int t;t=1;cin>>t;
    while(t--) {
        solve();
    }
}